How is this for mounting an ACME leadscrew? The bearings would be ABEC 7 skate bearings.

Both ends would be mounted the same with nylon locking nuts on the threaded portion of the shaft. Before tightening the nuts, I'd bolt on and tighten the stretcher across the uprights. Then I'd tighten the nuts to tension the leadscrew.

Exactly how much torque I still have to figure out as the skate bearings aren't going to take a lot. Probably just enough so that the kerk nuts don't groan during rapids.

Cams will be along shortly to flog you into submission.....

I think your design is fine but your bearing selection is going to make or break the performance. Considering you are mounting an acme screw indicates the lack of super-duper precision, therefore I think the arrangement is perfectly acceptable. I think it would be better to use a set of AC bearings mounted DB for the thrust loading and preload but these are going to cost you more as you likely know.

Let's see how badly Cams beats you up over this, but I am voting for sticking to your plan. It looks good to me.

Scott