I have an upcoming flight from EWR-YUL, and I booked a BE fare (super short flight, figured I didn't care about a seat assignment on an E175 where everything is a window or aisle anyway). I'm normally a DL flier, where BE includes a carry-on, and I totally forgot that the UA fare doesn't include a carry-on bag for non-status pax. That's what I get for multitasking when I clicked through the confirmation warning for a BE fare; oh well.

I need to bring a regular sized carry-on, so I assume I'll have to pay the checked bag fee - but here's my question. If I pay the checked bag fee at check-in, any chance I could bring my carry-on sized bag to the gate? Will the GA still try to charge me an additional $25 if I've already paid for a checked bag? Or should I just cut my losses and go to the counter kiosk to drop it off? I really wanted to avoid standing around at the carousel at YUL for 20 mins if I don't have to, but not the end of the world if so.

Thanks in advance, UA FT hivemind!