If you have experienced knowledgable people do this stuff... it is alright.
And by the way.. they "bore" it out... they don't drill it out.. it is a very much more refined and controlled and more accurate operation.
.. and usually you don't want to remove material from the "floor" of the throat.
But for someone without much knowledge to just go sticking a crude as hell drill bit in there.....oooooh!...don't do it!
If you go just a tad too big... guess what?... your butterfly (or slide) won't shut off the air flow.. your ped will run at "half throttle" all day long.. and will not go any slower.
Sound like fun?
I think you are better off to buy a larger carb from one of the moped shops... then you have 2 good carbs... not 1 that is now junk.