Scott is correct.
I use the same one piece engine mount for my MTX4R, and in both my RRRs.
The 15 engine should have the same size dem. as the 12.
So if you want, you could use a Kyosho mount in the Mugen with either a 12 engine, or a 15 engine.
You ust would not be able to run the 15 engine in a race, other than maybe a club race.
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