Originally Posted by
Dereck
I don't want to appear to be tossing buckets of water on the fire of your enthusiasm, but unless you derive more pleasure from math than balsa dust, just get stuck in and build this model of yours, get it to the flying field and experience the greatest thrill in our hobby - test flying your own creation.
...
Go forth and make balsa dust

Absolutely! Do it, do it!
The maths is a start and a useful check at times but don't let it get to you!
It
can bug you if it keeps coming out wrong though...
Just a thought... when you did: span x chord, did you multiply it by two? Don't forget it's a biplane!