You've got the right idea for belts, we covered power transmission(belts, chains) in my last bout of schooling, Im an Apprentice Millwright.
What is your spindle motor rated at? The PolyV is a multi ribbed belt, usually used for high power applications. I think you could use a regular Vee belt, or the more modern deep groove V belt or narrow V. Classic V belts are sized by letter A,B,C, etc, narrow Vs are 3V, 5V, 8V etc. They taught me about belt construction and applications but not where to buy them, typically I dont purchase parts at work i just install them. My textbooks are in storage, when I get at them I can give you some more details but I wont have access to them for a few more weeks. The biggest drawback of the V belt is how much tension you need to put on the belt, as the wedging action of the belt into the sheave is what transmits the power. Too much tension or excessive vibration will go right into your bearings so you need to be sure of your alignment and tension settings.
Timing belts will be good on the servos, as they have very low backlash. Just fit the widest belts you can.
Have you tried using gas shocks to assist opening the gull wing on your 9x20? If those dont help, build the door out of aluminum to save some wieght.
This fella has done some nice work on his build, check out his console!
http://www.cnczone.com/forums/vertic...-progress.html