Mark,
Thank you very much for the input! So, 200 in-Oz motors would be the max I need? I think that's the size I am seeing in the industrial sized outfits (hotwire direct). I will probably do some calculations based on the screw I have, bracketing the frictions I think I will get based on materials. Then I need to consider the torque I need for self locking on the vertical towers. Maybe I can get away with smaller motors if we go 3.5 mm/sec. I am ok with slow, like I said I'm building 1 airplane, but I also want the experience of building this machine. I am just as interested in the journey as I am the end product : ). In the end I want a useable CNC hotwire with decent accuracy (I will add fiberglass and sand to the finish surface, so perfect .001" accuracy is not needed) that produces smooth surfaces. After I build the plane I could start making cool models with it anyway or help friends with their projects : ). Anywho, thank you for the input, and I am glad to see others that tension their wires with the air cylinder!

-Chris