Assuming you're on Lake Erie, you probably are using VC17? Good stuff, and it goes on thin. If you search this site you'll find recent advice on how to apply it. I use about 2 cans of the stuff on my Catalina 309 (31 feet). I tend to have a little left over, which I save for the next season.
I do a thin coat every year.
I would say that no, you don't really want to skimp. Unless you like Zebra mussels and algae on the bottom of your boat. Go ahead and paint right up to the edge. Tape it with the blue tape, of course.
The cost of the vc17 brings pain, but if you want to feel better, just check with the marina and see what they'll charge to do it for you
. You save.
Depending on how far you live from where your boat is, you might want to get a second can and see if you need to open it. If not, return it (checking store policy first, of course). If you need a can and a half, that's just the way it goes.