hi vikash, not sure what happend to my post... 701HDV ill assume your using a pretty tubby camera on that, a builders level would be all over the place with that much weight on it, if you tend to film indoors then building a heavy rig isnt to much of a problem... if you go on solo missions out and about though i wouldnt right off the toothed belt or wire option, maybe even 2mm dyneema, it will help you keep the weight way down,, i was also thinking of rebuilding mine using two carbon tubes for rails (most of my stuff is in the mountains) maybe 15 or 20mm OD
ps: if you do give the rc servos a try you need to remove the feedback pot gear to get the servo to run endlessly in what ever direction or speed you dail in

have you got any of your work on vimeo?