We strongly considered emulating 1551's Regional-winning arm from 2010. Oh, and then we did that, with some modifications, because, well, emulating a prior success seemed like a good idea.
We used Bosch Rexroth extruded aluminum and delrin sliders on an aluminum carriage, on a fast multi-start screw driven by a CIM. This year we're going with two CIMs and some constant-force springs (because we learned some things from 2010!) The drive mechanism is *heavy*, but we think it's necessary to ensure a stable, smooth, efficient climb.