Really simple actually, as long as you have a decent drill and bit.
I drilled pretty much exactly where the mk2 routing is, just a tad offset as this meant I could get a better angle with the drill, and it also looks neater. Drilled out with a 3, then an 8 then with a 9 at a slight upward angle into the seat tube. Filed outside and in. Popped a Halfords wiring grommet in and fed the reverb tube through. I also drilled a small drainage hole in the bottom of the BB as whenever I take the BB out there is always sludge in there, guessing it’ll be worse with the new stealth hole. This is something that has been done on the mk2 and on most other bikes so I’m pretty confident it’ll be fine.
There’s a better thread out there showing the process on a Shan. I didn’t need to bother taping and centrepunching though as the aluminium is quite soft compared to steel.
Anyone who wants to see pics feel free to email me