WHen I say snubber in this case, I am referring to any kind of discrete device like diodes or R-C. DId you only have the main capacitor? YOu didn't have any diodes or anything?
I am not certain if I need snubbers, but I am uber paranoid about it because it's something that's very dependent on the layout and can't be predicted very well ahead of time. If it ends up not working, then I'm out $1k or so.
The best I can do are some realy crude calculations:
20nH/inch of PCB traces, 10nH source inductance, with 50A, and my rise times of 200ns with V=L*di/dt just tell me a spike of 25V is possible assuming the motor inductances are completely supressed by the main snubber. My thermal calculations tell me each MOSFET can only handle about 10A (since I'm trying not to use heatsinks and it suits my purposes anyways), and since the MOSFETs are daisy chained along the same trace I went and added up all the inductive spikes from each trace all the way to the MOSFET at the end of the daisy chain (ie. V = Ldi/dt with 50A, then 40A, then 30A...all the way to 10A, and then added all the Vs up to get the largest voltage drop).