Here is the 88mm; I just cut off the original and drilled 1.5mm (1/16")
Popped the brass replacement in with a tiny drop of SGlue and left for 2 mins; done

The 20mm is a little tougher and needs a steady hand; i cut off the plastic; and drilled with a 0.024" drill (#73)
I used a pin chuck; and just took my time; but it was still done in about 3 mins for the drilling; keep turning the plastic as you go deeper to maintain a good hole in line with the part left Again a tiny drop of glue and leave for a few mins; the result is stunning compared to the original plastic












































