Im in the process of building the flaps on my Brian Taylor typhoon i tried sevros, but ive opted for bellcranks in the end, ive found as long as the flaps fit well and move well and there is some friction on the bellcrnks, they tend to work after a bit of playing around.

What i have found though is that if you use bellcranks the outer sections need more movment on the bellcrank to keep up with the inner ones.