It has some flex to it and with logs in the real world, they are shaped irregularly. If you trim the log with a saw first, so the mounts can fit flat on the log, then it's fine, otherwise you have to do a lot of shimming to make sure one part of it isn't unsupported and then flexes. I like the idea, it is workable, but it's not as good as the old guideboards I used to make and use. If it were stiffer aluminum, it would be. Still pretty convenient but requires a lot of care in setup and clamping it down correctly.It came with a bunch of all-thread and bolts that are theoretically levelers. They weren't shown in the original order and I think were supposed to make sure it had consistent support all along. But with only about and inch and a half of room to put them down or up to level it, they weren't too useful and I removed them. I'm just bolting on the plates to the log and you have to trim and shim to make sure they sit square.
Felicia Nussbaumer 
