Gecko 2xx "Nema 42 modification"???

Question for the group:

I Fired off a question to Geckodrives, but users on the list might also have
had experience with this one and I could use all the input I can get.

I purchased three large steppers on eBay recently (SIGMA 20-4247TD200-F1.3,
and hopefully I didn't make a real bad purchase) so I could start playing
around CNC-ing my RF31. The seller said that a previous customer used Geckos
with a NEMA 42 modification. The explanation I received was:

"These steppers work FLAWLESSLY with gecko stepperdrivers with the nema 42
modification.
I had a lot of trouble with intermitent stalling with drivers purchased
without the nema 42 modification."

"as it was "explained" to me, the nema 42 motor's are designed to run in a
different RPM / torque range. the Mid band stabilization circuit on
standard gecko drivers can get "saturated" causing that annoying motor growl
(phase lock) and subsequent positioning error. since replacing the standard
gecko driver with the modified drivers all my axis (especially the Y axis
which carries the beam) run perfectly. the Modified drivers cost the same
as the standard, but they do have a distinct label engraved on them. The
guy who developed the gecko driver is the guy I spoke with, and he was very
helpful"

The published ratings for the motors are:

200 step
540 oz-in @ 50 sps
635 oz-in holding
22.6 oz-in detent torque
5.0 Amp phase current
1.29 ohms phase resistance
2.2 mH phase inductance
17.4 oz-in^2 rotor inertia
10 lbs. weight, 30 watts dissipation, 8-wire

Anybody know about this?

Thanks all,

Paul R. Hvidston, N6MGN
ACKSYS Engineering
Upland, CA