BossHog,
First things first: What is your plan for grinding down the windshield? Windshields that are specifically cut for a Cimbria don't exist, which means that you bought a shiny new beautiful Sterling windshield...which won't fit without slight but unavoidable modification. A bunch of us are trying to figure out how to grind down the windshield. We will be eager to hear what your going to try to do and hear updates on your progress. What's your current plan for cutting down the windshield?
I definitely like your idea to strengthen the A pillars and roof section. I can't think of any drawback from having that extra rigidity (except for the pain in the butt of having to cut into those sections and fabricating and embedding the steel.)
It is interesting to speculate whether the Cimbria SS might be more prone to cracking of the windshield as compared to the first gen Cimbria. In the first gen Cimbria, the doors are quite a bit lighter and the roof section (between the hinges of the gull wings) is wider. I can tell you that my first gen car doesn't seem to have any significant flex in that area. My one Cimbria SS body -- which DOESN'T have a windshield in it -- has a considerable amount of flex just like you are describing. Interestingly, my other Cimbria SS, with an intact windshield, doesn't have any flex. ...but of course that means that there are thus stresses being "successfully" absorbed through the windshield.
I grew up around my dad who has built/restored about 45 to 50 sport aircraft. In each one, it has never ceased to amaze me how flimsy some of the pieces seem until ALL of them are brought together as a unit. Every little piece makes its unit stronger. There are virtually no pieces that aren't shouldering some of the stresses. It isn't 100% bad thinking to expect that the windshield might be expected to contribute somewhat to the rigidity of that system...up to a point, of course. And obviously, we're all trying to figure out whether that point has been passed in the SS.
There might be a design flaw that is leading to cracked windows. There really might be. But it is also true that it is not completely wrong to expect the window to contribute to some of the overall integrity of the unit. I believe there are a lot of convertibles out there whose window frames would seem a little scary (in terms of flexibility) with the windshield removed. (But of course, that's not a perfect example because, in a convertible, we aren't expecting windshield frame to support heavy gullwing doors.) My point is that, like you, some of us are a bit concerned about the lack of stark rigidity in the window frame of the SS. But it is unclear how much of that is a cause versus how much of that is a symptom of the windshield being cracked. I wish we knew for sure.
There is one nuance to mention: Letterman7 once pointed out how heavy the doors are on Fuzz's Cimbria SS, yet the doors on my SS are not heavy at all. Apparently some have an internal metal framework and some do not. I don't know if the metal internal frame was a quiet factory modification in later models or if Fuzz just happens to have a unique car in which the builder made that specific request. Anyway, my point is that different Cimbria SS cars might have different issues regarding the interplay of the doors, windshield, and roof/windshield frame.
I also wonder if it makes a difference if the previous owners ever drove with the doors up, like when parking or slow-speed show-boating for a crowd. THAT would put a heck of a potential load on the windshield and fiberglass frame. THAT is a very bad idea.
When the doors are down and closed, however, the bulk of the mass of the door is quite low on the door. With the door closed and latched properly, the roof can't flex downward because the door is rigid enough to transfer forces mainly down into the sills on the side. With the doors down and latched, there should be virtually nothing you could do with regard to driving conditions that would ever make the front top corners of the door tip downward. And I don't think there is a problem with the static load when parked with doors up. I wonder if some owners were their own worst enemy and were too liberal in moving the car with the doors up. Perhaps it isn't an inherent design flaw beyond not having enough buffer against carelessness.
That said, are any of us totally convinced that the entire body of the Cimbria SS is torsionally rigid enough? I mean, the Sterling has essentially a huge, strong D-section of body that runs up both sides of the cockpit. It's rock solid. The first gen Cimbria has a higher side sill than the SS, so it at least has SOME of the rigidity of the Sterling. But then there's the SS, which has a very low side sill at the door. With a low side sill, very narrow roof section, and essentially a stock Bug chassis, there's just not a lot of extra torsional rigidity.
I, for one, would like to see a beefed up perimeter chassis on any VW chassis on an SS. If you're tearing down your car enough to justify doing so, you might consider reinforcing the actual chassis on the sides as well as the A-pillars and roof.
Anyway, in summary, I think that the roof and window frame of a Cimbria is considerably weaker than a Sterling due to structural differences between the gull wings versus the canopy. And I think the roof/window frame of a Cimbria SS is weaker than a first gen Cimbria due to reasons stated above. And yet I'm also still going to stubbornly hold to my theory that a lot of the broken windshields on Cimbrias that come up for sale is simply because they were damaged from random, stupid reasons and there has been no source for replacements for 25-30 years. I've seen Sterlings and Sebrings for sale with broken windshields, too (and their canopies are extremely rigid.) The difference is, you can still get a replacement windshield for a Sterling and Sebring.
But I'll end by repeating one of the my first points: I think it is a fine idea to try to strengthen those elements of the SS. Please keep up apprised of your strategies and progress for doing so. If executed well, it will definitely benefit your car, and there will be owners over time who will probably want to try the same. *thumbs up*
We have a few good leads, including but not limited to the one above. It's just a matter of finding a company that can trim an existing Sterling windshield in the manner we need. (More to come...)