Carlos,

So you do race the T-34.

If so, the correct load for the engine would be a 10x8, or a 10.5x8 (better), so you can get a speed advantage from the higher prop pitch. Even a 10.5x7 is preferable to the 10x7.

The 10.5 diameter will improve your thrust by over a pound, compared with the 10x7 you now use, despite the RPM reduction.

You will have to obtain a small stock of Bolly props, because APC doesn't have these sizes. See this web site for North America:

http://www.bollyprops.com/index.html

My T-34 is my first and has been flying with a minor mishap, or two, but no major crashes (thankfully), for nearly 3 years.