I removed the seat and pet carrier, and I've found the carb. Pretty tight in there. Removed the airbox and that opens things up a bit. Here's a photo of what I see with arrows pointing to what I *thought* were the drain screw and line:

I hooked up a longer piece of fuel line there that led down to a bucket, and backed that screw out a few turns, and it started draining...and draining...and draining. By the time I'd collected maybe 1/4 of a one-gallon ice cream bucket or so, I figured I must've been doing something wrong

If someone could please chime in here, I'd greatly appreciate. I'm a long-time scooter rider, but first year w/ a buddy. I'm used to working on vintage Honda step-throughs (Cubs, primarily) -- which have their own unique challenges, but the carb is extremely accessible and I'm a bit flustered after spending the better part of an afternoon out there and not getting this done. Usually the carb drain is on the BOTTOM of the bowl, but there is literally no clearance under this carb, I don't see how you could get under there without removing the carb completely.
Thinking I'm going to have to install a manual petcock next summer, would make things a heck of a lot easier. Turn the petcock off and let the bike run until it uses up what's left in the bowl, presto, done.
Thanks a million for the help!