Can anyone give me the appropriate equations or other advice for building a set of winglets similar to those found on the BTE Flying King, aka "STOL wingtips"? I am getting ready to build a Goldberg Falcon III, and it seems that STOL tips would be a welcome addition to an excellent design.

Would STOL tips be effective in an airplane of that size? Would adding STOL tips cause unwanted effects such as yaw control problems, poor roll control, or excessive drag? How much area should STOL wingtips encompass for maximum increase in low-speed lift with a minimum unwanted side effects? What is the best angle w/r/t the wings themselves for the winglets to take maximum effect?