Does anyone have any info on modifying a Senior Telemaster to add flaps. I have heard several folks recommend adding flaps because of the significant "float" a telemaster has in ground effect when landing. Are the flaps really needed? If so, how much of the existing aileron is modified to create the flap? What length flap vs what length aileron?

It sounds like what you want are spoilers. The Telemaster is undoubtedly a floater, adding flaps will just make it float even more. Basically, neither is needed, but if you really wanted to do it, I would use about 1/4 of the root side of each aileron as flaps/spoilers.

Personally I wouldn't add flaps to another telemaster (senior) if I built one. It floats as it is and like MinnFlyer said it makes it float more. Maybe spoilers would add a different view to things and flaps could be made to go up and be spoilerons. I took about half the dihedral out of mine too and made it a taildragger.