*hi-ya* The ONLY way to treat spider (stress) cracks is to rip the area down to the glass fibre and fill, sand, prime and paint, anything less and they will pop up again in a short while ruining your paintwork, again. Use a flexible two part filler like Plastic Padding elastic Isopon P45 or what ever is available State side, plastic primer, undercoat,t top coat, clear, , it isn't quick and it isn't easy.*sigh*