Disclaimer: 

The base is designed to have a tight yet removable fit to the catch cup. Repeated installation and removal of the base may scratch the paint on the catch cup.

Features:

• Designed from a trace of the catch cup geometry.
• Top lip matches the cup and clears the handle.
• Base does not collide with the handle when grinding.
• Slot on the bottom helps with catch cup removal from the base.

Instructions:

Print the fit test piece first and adjust the horizontal expansion or scale in slicer until the piece can slide up to the top of the catch cup.

The CAD file is also provided for easy remixing.

Big thanks to @longpvo of EAF for the nice pictures.