This seems ill-advised to try to use capped nuts on the studs. Even if you measured and compared to the length of the stock wheel bolts to determine the ideal length for the studs, using a capped nut would make it difficult to torque your wheels securely. I wouldn't want to be your insurance agent!
I see what you mean if you use studs with a smooth end. There must be studs with thread to the end though?
