Oh, I see. I definitely wouldn't want to fill the board with resin. Although, with the sanding sealer liberally applied, I'm fairly certain it's airtight. I've had it in the water already, and it didn't absorb anything anyway. As far as deforming goes, I've attached a picture of what it looks like on the inside (has a plywood skin on the deck now). I can stand on it if that's any indication. 

Yes you could do both top and bottom at the same time but you mention it's hollow wood so infusing may not be the way to go (one little crack in the finish and it will suck all the resin into the hole and that's if you can pull full vacuum on it and prevent the core from deforming).

I was just having a gander at your charming resin infusion starter kit, and was wondering if it would fit my needs. I've only ever done wet hand layups in the past, so jumping straight into resin infusion vacuum bagging is a pretty big step for me.