Sikaflex 512 has now been replaced by 522 - the sealant is exactly the same but just an updated version. Sikaflex 522 is both an adhesive and sealant making it ideal for caravan, motorhome and trailer repairs as well as DIY fitting of caravan vehicle accessories.

Sikaflex 522 Caravan Adhesive Sealant - White - Camperlands UK Sikaflex 522 Caravan Adhesive Sealant - White - Camperlands UK

I always liked W4 mastic, comes on a roll in varying widths. Used it on various jobs including top rails when we had MH.

Sikaflex®-522 cures by reaction with atmospheric moisture. At low temperatures the water content of the air is generally lower and the curing reaction proceeds some-what slower (see diagram 1). Multi purpose hybrid adhesive sealant with high weathering, ageing and mould resistance. Suitable for the sealing and bonding of various applications internally and externally in caravans and motorhomes, including skylights and aerators.

Sikaflex 522 (White) (REPLACES SIKAFLEX 512) - Magnum Motorhomes Sikaflex 522 (White) (REPLACES SIKAFLEX 512) - Magnum Motorhomes

Very easy to use but doesn't seem flexible enough to me and may not fill the gap completely although several users appear to be satisfied. This is a highly recommended product, ideal for installing windows and rooflights into panel van conversionsThis approach seems best, as you can put plenty on, smooth it over with normal tools before it skins plus it remains plastic over time (supposedly) ? Also stainless screws (e-bay, get the right length and head shape) would be useful rather than anything that may corrode? Uncured Sikaflex®-522 can be removed from tools and equipment with Sika® Remover-208 or another suitable solvent. Once cured, the material can only be removed mechanically.