Yes, I have the Graupner Sukhoi SU-31. Graupner kit is outstanding. And so are the flight characteristics. I have powered my Sukhoi with an OS 70 Surpass.

The engine gives the plane enough power, in my opinion. Maybe not enough for a hover, but for normal aerobatics I couldn't notice any problem.
It files very good. The only problem i have noticed is that the screws for the cowling-, and the belly-pan came loose in flight caused by the vibration.

Here are some pictures of my Graupner Sukhoi