I have used the tourtech holder and the MD holder. The tourtech did work but you could tell that if you had a problem...you would have a hard time fixing it. I do have a nearly new tourtech unit I got for my 950 a while back. It has the metal gears...but there are a ton of gears in there and it doesn't look like it would take much to cause a problem.
I found the MD to be very easy to use and the only problem I had was due to me winding my paper roll too tight...this causes the rubber bands to slip.
I did some road book prototyping a few years ago but never finished. My idea was to have two driven rolls and one paper guide making things as compact as possible. Had an idea for using a single chain and 2 1 way roller clutches. Never built it but could do so someday