From my own experience the flaps will work fine up to about 25 degrees and after that the adverse yaw gets to be too much to deal with unless you use rudder at the same time. Past 60 you can forget about any aileron action that works normally at all.

But most of the extra lift occurs during the first 25 degrees. After that it's pretty draggy with any further increase in lift.

Be sure to check it out way up high. You are basically increasing the camber of the section and along with that comes an increase in pitching moment as I understand it. The stab may not have the area to deal with the extra load.