Size was always the problem with the 109 in this scale. To keep wing loading down, you must be very light. The .25 FX was well suited for the bigger planes that came along later like the TA 152 and the big Japanese stuff.
Not sure with the 2548 rules or whatever the RCCA has dreamed up recently to try to generate interest. If you are over 38" span, the .25 FX would work. Closer to the scale 34" span, I would go with a hot .15 like the Magnum.