Fine-angle wedges, cylindrical partners
The partners on my boats have mostly been made from metal, steel or aluminium, and they have been cylindrical with a rod welded to it along the upper edge. This means that the wedges get a little dented, but after gently hammering them down after a few trips, they stay put.
On Ingeborg I made the wedges with very fine angles. The fine-adjustment of the mast rake (plumb) was actually done by shifting the mast step a bit back and forth. This let me make the partners with only 20mm clearance for the mast, and all wedges could be made next to identical.
At the mast step, the fit is so good that I have only added a couple of thin wedges there. This may not be good enough for offshore work, though, but the mast has at least been secured from jumping out of the step...
Arne