L6470 dSPIN Acceleration problem.

I have been using the L6470 dSPIN to drive a stepper motor.
I had a problem with acceleration that had me stumped for months.
Motor would start slowly, vibrate a lot then run at full speed ok.

The problem was Kval settings: 255 = full power, default setting is 41 = not enough power.
The Sparkfun demo code I was using set KVAL_RUN only and I wrongly assumed Acc & Dec Kval would default to full power.
My code now includes -
dSPIN_SetParam(dSPIN_KVAL_RUN, 100); // 0 to 255
dSPIN_SetParam(dSPIN_KVAL_ACC, 255); // 0 to 255
dSPIN_SetParam(dSPIN_KVAL_DEC, 255); // 0 to 255

I have not seen this problem posted before (believe me - I looked!) which probably means other dSPIN users are a lot smarter than me but this post may help somebody.