I've just put together a project Beeman R1 in .22" calibre. At this stage, the internals are pretty standard apart from the spring, as I've dropped in a 14.5mm i/d spring with a bit more pre-load. Currently running at full stroke length, she's at 11.7ft/lb with FAP, but a bit harsh on cycle. The problem lies, I think, with the transfer port; measured at 4mm. I'm not sure if this was US spec' or if someone had previously tweaked it up. So, I'm thinking of a tp reduction to 3mm. Do I:

A) drill out the tp and tap it to add a drilled out grub screw and glue it in? I've done this before with an HW80 with good results.

B) get a sleeve made and drift it into the existing tp?