These DCJ's use a 5mm bearing. They should drop right in, although I have not had the 6.1 caster blocks in my hand to test them. With the 6, you have to shave the caster block a bit to make them work. I have not had increased breakage due to this though.
We can certainly look into the Schumacher. It is just a matter of getting some schumacher drive shafts in my hands.
At the moment, we were not really planning on different lengths for the TC6. However, if we see that there is enough demand for it, we can look into it.