The method I use involves putting in lag bolts every couple of feet to support the 2x8 or 2x10 board straight and level. Takes maybe a little more time to set up than the store-bought track, but the board is under $10, and I can still use the board for something else. Never had any issue with a bow.
That sounds like a plan that'll work. Cool beans I'll be in business sooner then I thought I'd be. I just bought a homelite 38cc chainsaw for $70 and ordered a beam machine to attach to it. Only a 16" bar on the saw but I figure it'll save me a lot of changing back and forth between mills. Now I just need a few log dogs and a coupla peavys and I'll be ready to build my first lean-to. Gotta wait until mud seasons over with but I have a place to build one and a couple friends willing to help. Going to scope the place out and tag a tree or 4 this weekend. Yes I'll post pics and video.