OK, I'll start it: DON'T. You'll hate the results, and they can't be 'fixed'.
(Batter up!)
Not strictly true, but, I have 40+ yrs working on motorcycle carbs
If you don't have 100% understanding of how your carburettors work and what is going to need modifying, don't mess with it, you can't make it better (particularly on a stock engine)
Anyone who says it's 'fine' by just fitting bigger main jets and moving needle obviously doesn't know how the bike should run
It isn't impossible to get right, but, it isn't as easy as a lot of people make out
If your not comfortable drilling holes in carb's (and even iff you are) it's best to leave stock airbox in place
If you do a quick search you'll find out how many people reverted to stock
Personally, I very rarely increase pilot jet size, the stock airbox has virtually zero restriction at idle~3,000 rpm so increasing pilot jet is compensating for a problem somewhere else.
If you put bike on dyno with gas analyser, you'll see very rich mixture.
The Gary Nixon bike isn't stock, apart from the 836cc motor you don't know what cam is in there or what porting has been done, plus, just having a video of running bike is worthless, the only thing that could be useful would be the printout showing fuel curve and HP/torque