Paul,

You should be fine with the gear and the legs -- it's designed to have a very minimal clearance.

As for the coupler, you definitely want the thrust bearings and clamps around the bearing block -- otherwise your motor bearings end up absorbing the thrust load, which is not good, as they aren't designed for these sorts of forces. However, you can potentially thread the ACME directly through the bearing block and skip the drill rod to save some space. The only issue with this is that the thrust washers sometimes fall down in the grooves of the screw, which is not so good, People have gotten around this by filling the threads in this portion in with epoxy,

I also now have helical couplers (1/4 to 1/2) for sale that are shorter than the lovejoys and zero backlash (Lovejoys have about 0.002" of backlash). I'll put them up on the site today.

Ahren
www.cncrouterparts.com