[GeeTwo]

We're using 2"x1"x1/8" aluminum c-channel for the frame and roller support. Since our height restriction is constant this year (don't have to be shorter at startup or go under some bar somewhere), we went with a single-stage lift rather than the two-stager shown above.
To keep the lift plate level on the roll axis, we're using two chains rather than one. To control pitch rotations, we've made a "double-decker sandwich" of teflon and aluminum. The center piece of aluminum is shorter than the others, and the c-channel frame fits into this groove. There's about a quarter inch of left-to-right play at the center that curves up to about half inch at the top and bottom. We're hoping that'll be enough to prevent binding. If not, we'll cut out a shape similar to half of a woodworiking biscuit from the central plate and put a matching piece of teflon there. Should that fail, we are considering rollers made of radial bearings mounted on bolts: two bearings on each side, all inside the C-channel, with the top one meeting the c-channel on the front face and the lower one contacting the back face. If we go to rollers, we'll have to move our limit switches, which are roller switches mounted inside the c-channel.