Hey guys, help me out here just a second.

I'm building a tailess plane powered by a .15 and I need your help verifying the balance point.

36" span
8" @root
5" @tip
2" sweep @tip

I'm thinking I should balance it at about 20% MAC

using http://www.palosrc.com/instructors/cg.htm
I get the result of:

MAC: 6.62" @ 8.31" from root
Balance point @root chord: 2.25"

When I plot out the CG location it doesn't look right.
I would appreciate if someone better versed in the science of aerodynamics could double check my work please.