Dave,
OK, will have a look at what I could do there.

Clive,
Cheers, I don't know if this is going to work but it's worth a shot to see what happens. I'm only going to fit them to the Y axis to see how it goes. I have some spare nuts to do the X axis as well.

I have some belleville washers on order in case the spring washers don't work out. It will really come down to how much speed I loose on the steppers due to the extra load causing them to stall out earlier.