We've installed ipe decking on 1 1/2" sleepers over a rubber membrane balcony using IPE fasteners and are now having a problem with the wood twisting and shrinking. We had sealed the ends and the face side only and from what I've read it's no necessary to seal the bottom side of the wood so you can let it breath. Is it possible that there is no air circulation underneath because there's only an 1 1/2" space? We have installed this before but in the screened in porch and it looks great but this is a balcony that has a lot exposer to sunlight. Any help is greatly needed. Thanks