I had a TT-61 Pro on a 60 size trainer. I mostly used Omega fuel with 10% nitro and 17% oil. I tried the following props on it:

11x7 - worked fine for takeoff and flying but my engine idled fairly fast at the time and my instructor usually had to kill the engine to get it to land.

13x5 - when the engine was very new it tended to overheat with this prop. Never tried it after the engine was fully broken in.

12x6 - seems to be a good 'all around' prop for .61 two stroke engines. My trainer would land with this prop and it seemed to give a good mix of speed and power.

13x4W - This prop made the trainer feel very powerful. It seemed to almost jump off the ground when I gave it throttle. One negative was that it took a higher throttle setting for just flying around so it used more fuel per flight. I liked this prop on my trainer but it was to expensive to use at the time. I was trying to learn to land and tended to drop the nose at the last second. The "wide blade" props cost $8 each. I broke 3 in 1 day so I went back to the 12x6 that cost $4.