Gearbox Outer Cover Screws

I've started this thread so as not to derail Jim's thread about "Thread Inserts into the Norton Head" - although that's what reminded me.
Many may already know this but anyway, just in case...
Of the two AMC gearboxes I have reconditioned to date both had some dodgy (1/4" BSF - fine) threads to locate the outer RH cover.
Consistent with Jim's advice in his thread, I helicoiled all screws to 1/4" BWS (much coarser). Gave a much stronger result aad same screws as timing cover.
I think AMC stuffed up using fine BSF into alloy

I did all five in one of my bikes with stock UNF, I have a simple rule, use the longish coil that will fit so always use 2D or 2.5D if I can.
There is no way they will pull out under sensible tightening of the screws.

I think a lot of folk use 1.5D coils (Even the disk front hub has UNF and yes I put 2D in there)