I have a 19mm PHBG Del on my AV10, then again, I have a Polini kit...
In my experience, you'll want to be dialed in at about 1.3mm or less. I'm currently at 1.1mm.
A 21mm carb might be overkill but what do I know, I just run a 50cc race bike. I doubt the euro kit and your setup would take full advantage of the 21mm carb.
Leave the CDI in, get it down at or below 1.3mm btdc, open your reeds up, make sure that your intake is meant for two pedals and not four (this will cause you to have no low-end and force you to run a leaner setup), and run 50:1 if you are doing synthetic on your break-in. You will gum up your rings and run hotter doing 32:1 in my experience.