What would you consider small Brian? I'm currently stretching some 25x10 panos and although they're not as easy as the larger canvases, it's not bad. Are you suggesting that the thicker canvas 'should' be used on larger pieces?
It isn't just the size of the frame, it is also the depth of the stretchers. When buying canvas for painting (oils, acrylics, etc), you can buy as much as youwant gesso it, and try it out - you can find out quite cheaply what works for your style, medium, and size. Unfortunately, with inkjet priting, you have to buy whole rolls.
And apart from anything else, you can't go by basis weight alone, more heavily textured cavas is usually thicker, and smoother canvas lighter weight.
Are you having problems with the canvas(es) you are using?