What material for Risers?

[fishmore2013]

I don't think mine will come out like that. What a great job! I did pull the floor up tonite and this is what I found, see pic
I am picking up 3/4 marine plywood tomorrow and will probably use the plywood to get the correct deck height.
Any reccomendation on which scuppers to use for through transom?
Thanks again to everyone replying, the expertise on this website is great.
Jon