RE: OS 46 powered TC31 the making...
Go with an 11cc pipe as the OS .46 likes them for some reason. Once you get it dialed in you should find that the X-450 or X-646/3 props might give you the extra speed that you're looking for.
If you use the big pipe that you have there, it's going to have to be muffled. I did some testing last weekend with a pipe that all I did was JB Weld a piece of brass tubing inside the stinger so that it runs as far as the fat part of the pipe. I didn't see any loss in power but had a much quieter pipe. I did drill out the stinger though so that I didn't lose any internal diameter once I put the tubing in. If it didn't work I could always drill the tubing out.