I have the BCA floating 18, used $200 blown 1x for fun, itís a bit small, itís fine for side country lift assist and packing a lunch. Get at least the 22 they work on compressed air cheap to fill. Iíve had my completely taken apart to do some sewing on it to fit poles...but with a 22L or larger...or smaller poles will fit inside.
18 is pretty small. So is a 22. 30-35 is kind of the standard for touring. Gives you enough space for standard gear, extra layers, food, water, first aid, skins. 18-22 is great if all you are doing is sidecountry laps where you just need minimal gear. That is one of the things I liked about next year's BCA line up. Choose what size bag you need for the day, zip it onto the airbag system and go.