Hello,
You could replace the CIMple box output shaft with a Toughbox Long Output Shaft (am-0211) if you turn down the hex portion of the TB shaft to 0.380" long. I have attached a PDF of what the final shaft should look like. Note: the groove cut into the TB shaft for the E-Clip will still be there, since you still want the shaft to be .500" thick on the round portion. If you have any further questions, please let us know!
-Nick
1.PDF