[macojoe]

That might work well??

But you will have to make sure you get the the ply to bend to the shape of the deck, and filled the right way so there is no pockets under the finished top.
From doing from under you avoid all them issues as any imperfections will be under and never seen.

You could also do from below and use some sheet rock screws from top to screw ply up, Then when finished remove screws from top and just need to fill the small screw holes