Depending upon the width of the board and where you put the rail shoulder/bevel you may wind up with a much bulkier rail than normal. It is possible to take it down very thin from that point, but it involves a kind of acute transition (hard to express this in words) that you don't see very often. And in a poly blank, that deck cut is going DEEP to get that out of there. Cutting a concave deck design out of a blank with a convex deck is a bit of a pain.
Chris Gallagher's G Deck is kind of what I was talking about re the acute transition. Last profile.