The problems I encountered with the SP's (3x 120's) were due to detonation hammering them, and anything connected to them, to pieces.
My investigation found that fuel, and run in time, were critical with these motors.
Also, the bottom end had to be set just right or mid range problems were encountered (vibration, detonation)
The 120's kept blowing the ends out of the supplied mufflers, and I did have my doubts about the cheap Chinese carby's being used.
When they are running right, big 4 blade prop attached, the pull like a freight train and have a very pleasing sound, quite different to other 4 strokes.

RCV in the UK have the best customer support I have come across. In the end they fully refunded me for the motors plus freight.
I still wish I could have sorted the problems I was having, the P-61 would have sounded ausome with 2 x 120's in sync.

A friend has a 60SP which went well until a mid air took him out on the 5th flight. We have just put it into his Ugly Stik and have yet to test fly it.
Again, vibration in the mid range was evident, but we are still running the bottom end rich which will be attended to during field tuning.