I considered the captive drawbar, looks like a good idea, but chose to go with the Belleville washers instead.
The RF30 has a 1/2" hole in the spindle, and the drawbar is 7/16" dia. You would need to bore the spindle 17/32" an inch or so deep. I don't have a drill bit that size, and when I envisioned myself standing on a stepstool trying to drill it by hand, and then tapping 5/8-11,( not gonna remove the quill and mount in the lathe to do properly) I quickly lost interest in that idea. Would also have to turn down part of the drawbar to 3/8" to fit through the bushing.
I wound up having to make a whole new drawbar anyway, so maybe it wouldn't have been so bad after all....
I have my mill mounted a bit higher than usual to save my back, so when the head is in the higher position it is a good stretch to reach the drawbar, so I wanted to avoid having to unscrew it altogether.
BTW, nice job on the "Cuppa Joe" mod, I have a 20 mm shaft and linear bearings waiting to do that to mine eventually.