Here's my opinion on your drawing.

5" is way too thick for the boat. !.5"-2" foam would be best. 5" will give you a higher COG.
I would aslo icrease the rake. Make it 6" back from the bow.

I''ve never built a .25 before....If I were to build one, I would make it 22" long by 10-11" across the bottom.