Our club has about 100 boats and about 40 of them run the proboat.
I run 8 proboats in my 6 boats, One of my boats runs 2 Graupner 700 12v speed motors with one proboat, the only problem I have seen is when someone tries to put more than 12 volts which they are rated for, or like I did once reverse the polarity on the battery.
Viper 900 motors are about 580 +- RPMS per volt and dont pull that many amps.
On this scale boat thread, a few stories down you can see my 109 with 3 motors and 3 proboat escs.
The one thing I do not like about the proboat escs is it is hard to get a slow speed from them.