I had Neville's setup done quite some years ago now, pistons, cam and clutch. At the time I had Ramair and Reband exhaust. Got 201 RWHP. You will like it.
Maybe when people purchase a Rocket, there should be a warning on it like medication:
"May have side effects"
1. Lust for mods and power gains.
2. Sore facial muscles after sustained silly grin.
3. Lengthened forearms.
4. Improved grip strength.
5. Puckered sphincter.
6. Ability to loose...
I would only tap down to the base of the existing hole, definitely not deeper into the casing. There will be enough thread (probably same as original with longer bolt).
As did mine, the casting broke where the length of the bolt finished. You can see 4 more thread depth which is still good. A longer bolt which is 4 threads more or piece of mind tap a few more threads and it will work.
I had similar issue with my RHS running board fixings after accident. You will find you can tap in a longer thread and use a longer bolt. Still do the epoxy for cosmetic purposes.
Shame Dave is no longer available. He was my go to guy. I have fiddled around with basics like lights, horn, seat, radiator grille, suspension, exhaust, oil and brakes but major internals......hmmmm, not yet. Good luck with your findings.
Old fuel. My lawnmower usually suffers from that. If I buy too much it goes stale and starting is hard. Makes you chuckle when you see movies where they come across fuel after a place has been abandoned due to zombies or Armageddon etc and it works fine, but that's Hollywood. Same as 1 fire...