Foamlock is slightly better than the 3M 90. The problem that most people have with 3M 90 is not knowing how to apply it. Proper application is the key. I wasted about 10 cans purely on product application testings. There is a exact set time, relative to temperature, to apply the product. Too early or too late, and the product is useless. This is the same for contact cement. I've had installers tell me contact cement does work. It surely doesn't work when it not put on right. Contact cement used to be $100 for a 5 gallon. Prices rose to $140. Where are you buying it for $20 a gal? I might have to go there.
Tuan