Area 51 ... New carb or rebuild & hints n#eeded

Hi, I've got an Aprillia Area 51 50cc scooter.

I would guess it's been derestricted as it's got an Endy power exhaust on it, which looking at the ads for them comes with power rollers, so I assume that they have been fitted. It goes up to about 40 on the flat & 50 downhill, but I'm a big bloke... 6 ft 1" and knocking on 18 stone!

Both top & bottom end of the engine have been rebuilt & are still being run in.

It's running on the standard carb ... PHBN 12 which needs rebuilding (I think they are 17.5 mm?).

Would I be better off performance wise rebuilding this & fitting with say a 84 main jet or going for a new 19 or 21 mm carb?

Would it be worth fitting a performance reed block / reeds?

Would I notice much difference if I plonked a 70cc top end on it?