It seems that the most popular ones are the Redrock Microremote and the RT Motion. The latter is the more expensive but then its quality is better by all accounts. So far though, I have only read about these and not hands on but I did as much looking into as I could and am now awaiting delivery of the RT Motion FF.
Has anyone hear used the RT motion. Looks great, I find that the redrock is kind of a POS, but real FF are far to heavy and expensive. This looks like it could potentially be a happy median.
I use 1 follow focus on all... lol Chrosziel 204 on my 5d, c500, arri alexa. I don't find the weight to be an issue since it adds stability on lighter cams.
I've never used a better FF. Even Arri's own FF systems are left at the studio most of the time. I find most of Redrock Micro stuff sort of cheap though I do have their cage for the C500.
I have been using Filmcity HS-1 DSLR follow focus. And i am very happy with this FF, cheap and well bulit. you can check following links may suit your requirement.
Proaim E-Focus DSLR (EF-DSLR)
Pro zoom and focus control Follow focus