I have one that is at least 20 yrs old, covered in Polyspan, crashed at least 50 times training kids, and powered by everything from a Cox medallion .09, Fox .15 slant plug, OS .10 and .15. Good flying honest plane, great for getting past the crashing stuff like reverse wingover, inverted, etc.
The .15 was too much, even propped down with a 8x3 or 7x4 it was too fast on 52' lines and to much line bow on 60". The .10 was good- but needed a bunch of tail weight- the Fox .15 with no muffler balanced good, but was a bit weak for good performance. The Medallion .09 was a really good combo- but suffered from tank draw issues w/o muffler pressure, and I did not want to drill the front housing pressure tap - last one I did that to cracked at the pressure tap.
Bottom line, you can put any of the engines you have on it and it will fly well, play with prop size and line length to get it flying at a good speed with adequate tension, ( .012 lines work great). Tank size mounting can be a challenge, but the small Hayes tank works pretty good.
Enjoy, and don't forget that after your Ringmaster- maybe a Shoestring or an Oriental will do you well.