Here is a simple, 10 second cure for the OCP manufacturing defect that all Gee Bees have when using a properly functioning 2S battery under normal flight conditions:
Using any pair of sharp scissors, clip a tiny 45-45-90 triangle from the trailing edge of each propeller blade tip. The two equal sides of the triangle are equal to one-half of the propeller tip's chord. This fix tests 100% good for OCP elimination, plus adds a bit of thrust and speed.
If you clip both tips anywhere close to similarly, the pieces removed are so small that there is no need to re-balance the prop. If you are concerned about prop balance and do not have a magnetic prop balancer or a set of magnets and a drill bit to re-balance (the Z8RC EDF balancing method (see Update 1) works great for props too), just mark and snip one blade slightly less so you know which way to adjust as you test balance by slowly running up the throttle.
How simple is that? Problem solved.
Complete Review: http://z8rc.blogspot.com/2011/12/umx-gee-bee-r2-bnf-flight-review.html