What material for Risers?

[fishmore2013]

I am making slow ground with an unheated garage in cold Connecticut weather, I flipped the cap Sunday-recruited my wife, father in law and fishing buddy. Glassed some spacers to the inner front hull to support the new floor. We had to reglass the top of the hull(someone used a sawzall on it?) to bring that up an inch and straight. More pics to follow.
Thanks again for the helpful posts.