Hibbert - regarding the pause you get at hand off between the idle and main jets.
Take off the carb top & look down it with the bike running on the stand.
Open less than 1/3 throttle - as you get close to 1/3 - it will do the pause.
What I believe you will see is a big droplet come out of the main jet feed tube that pokes in to the Venturi.
You can repeat this a couple times - I think you will get a visual of what's going on.
If your main jet is right at WOT - confirmed with plug chop - but it is choking out the hand off spot - perhaps the issue is your atomizer?
Meaning - you need to be either delay the moment that your main jet comes in to action by restricting its flow a hair - or when it does start to flow - it needs to flow less at that first point it comes online.
That's my theory anyway.
Right till everybody tells me why Im wrong.
Is there a BE something that would lean you out a little at that point to smooth that transition?