rocker table question

iam building a rocker table and was wondering what is better deck up. or bottom up? concave table or convex. i was going to use it with a vac bag. and load it all in the bag. ive seen both methods on this site.

Deck up is better because the bottom of your board is flatter than the top.

So when you do deck up your table will also help against twisting.

ah yes that makes more sense. and you can wedge up the nose if you want to add more rocker.(wich i read on berts vac. post) thanks for the help