If the roof is not leaking you could use that product on the seams. It wont be pretty on the edges and it could invite even more leaks. You have 2 options: Find a Sika distributor. They should have a product in a tube that will work on the edges. Other option is to cover the whole roof with the Impac. I am not good on roofs so would get a local tradesman to do the job. I would bet that in Maz. there are at least 200 guys who do this kind of work. AS Chris stated you can put down a mesh ( HD has it) and then put the coating on top. Not too thick. I don't like it as it is messy looking but here in Kino some of there really old trailers have used that product. I just remembered the English name: Elastomeric. You are aware of the rules for foreign trailers????
Moisheh