THINGS TO TRY
I have one with one of the older YS 120's (a friends rebuild pattern motor) and the power is not a problem.
One to two years ago "The Lady" was the sport plane to have at my field. There were five that had enough power up to find the terminal volecity for the air frame (110 to 112 MPH). One had a Webra 120 and the other four had YS 140's, with all of them it did not matter if it was 20% or 40% Nitro.
One thing you need to do if you have not finished yours yet is to fill in the open area below the horizontal stab with 1/4 or 3/8's balsa sheet so that you will have a greater area to glue to. That is the only week point that we found, the other things mentioned are done for the larger motors anyway.
Two of the fast guys went to deeper ailerons (3" to 3 1/2") and did not have a problem with flutter, but could they tumble in the air or what (just a food for thought)
I still have mine and the others have sold theirs and gone into the 33 and 42%'s
You will find that "The Lady" makes a great windy day bird, as landings are rock solid.
Take care Jim