If you find that the head rattling noise isn't at the lower speeds and seems to increase above 2000 RPM, it is often the top of the drawbar hitting against the side. This maybe because when it pulls down it may be off center or the mass at the top causes it to slightly oscillate and hit the side. I have machined several different spacers for the drawbar with a larger diameter and also a small nose that centers the drawbar when tightened. Most recently I machined a bronze cup type spacer with an ID of 7/8" OD 1" that fits over the rod head from the bottom and also use some high viscosity grease that will not flow or run. Rattling noise was significantly diminished. It is a bit finicky to get it all setup correctly, also that the top drawbar shoulder is the specified 0.050" below the mounting surface for the Torque-Rite.
I always need to have the quill up and locked when ejecting the R8 arbor/collet, probably because my return spring is not set very high and there is very low friction. Another thing to note is that when you switch out of back gear make sure you turn the spindle a bit by hand until the back gear lever snaps into high gear position otherwise you can damage the engagement spline gear hub on powering it up.