HSS 57 and HSS 86 closed loup stepper drivers

Has anybody worked out the optimum timings for these generic closed loup drivers?

I have changed my settings from the basic in stepconf (5000 -5000 - 20000 - 20000) to 500 - 500 - 5000 - 1000 and gained a big improvement in the acceleration on the HSS 57 drivers. The HSS drivers do not show much improvement but the are driving the knee of a myford VMC with a 8N/m 34 frame stepper at 30mm/sec and 100mm/sec acceleration,

The 2.2N/m on the x and y axis have improved considerably to 38mm/sec and using the test in stepconf up to 600mm/sec acceleration. In use I am using 350mm/sec acceleration.

I am using the basic 400 steps to rev and 3/1 reduction on the X and Y and 4/1on the Z.

I have been unable to use micro stepping as I get a joint error every time - bit of a pain as I have to dismantle everythinge to change the settings.

Any advice would be appreciated.

Thanks

John