Gary, the sensors I used were pretty much the same as the ones in the Crystalyte motors, which are Honeywell SS41As. I actually used the slightly more expensive SS411A sensors, just because they were the only ones in stock here in the UK. Digikey stock the SS41A sensors, part number 480-1999-ND.
Methods, my controller is set for full speed, I just have the three optional switched speeds set for 33%, 66% and 100% and the limit speed set to the maximum, 99%. I've been running it with the high speed wire grounded, so am getting full speed. Playing about with it late last night, I can detect some delay in the response, I think. It's partially masked by the stiffness in my throttle pot though, so it may well be that I'm just not feeling the lag the same way as you are. I'm pretty sure that there has to be a way of changing this in the controller firmware somehow. It's a great pity that the programming interface doesn't allow user control of the soft start ramp, like the AXE controller programmer does.
JEB, I did a rough check on the 'scope after swapping out the FETs, but didn't see anything awry. The new FETs (IRFB3077) are pretty close to the original ones in terms of gate charge, so I wasn't really expecting to see any difference (other than much reduced resistive loss from the lower Rdson).
I should finish getting the motor modded tonight (UK time!), with luck, so will report back on how well it works wired in wye.
Jeremy