Flyer Arm Brace for higher RPM
Full disclosure I have not tested this yet.
This part should allow spinning at higher RPM for finer yarns at the sacrifice of a small amount of bobbin space.
The 4 1mm deep x 4mm diameter pockets are for magnets to hold the halves together.
Print 2x and flip one when sliding it onto the flyer rods just inside the bobbin's far end-cap. They should mate together magnet to magnet.
Additional materials:
8x 1mm x 4mm Neodymium Magnets