Exactly what Lapo said, the plans as pdf's are all over the internet as well as the pilots guide.

From what I've learned combing through here and the QTalk archives is that the belly board mod is unnecessary on a Q1; adding hp increases rate of climb but not so much cruise speed; you can dream about changing the canard but don't; better breaks are a must as well as a proper alignment; if you actually want to fly it then you'll build the GU with vortex generators.

I think the important question is what modern foam to use.