I’m one of those that replaced both TV and TM wiring with 8ga. With the refrig. on 12v, my MorningStar batt monitor shows a slight discharge at idle. At 1200 RPM or more it shows a good charge, depending on the state of the battery. On the last four trips we made, I checked the batteries at the start and end of each run, they always had more charge when I arrived at my destination than when I started out. I can’t argue that 2ga would be better than 8ga but I think that if I were to do it again I would go with 6ga at the most. I only replaced the pos wire and use the hitch for ground. With everything hooked up, I jumped the TM & TV batteries with a length of welding cable and couldn’t see any improvement so I just stayed with only replacing the pos wire. The length of the TV and TM model would have to be considered. There is a good calculator near the bottom of this site to determine what size wire should be used.
http://www.powerstream.com/Wire_Size.htm?nowritefs
Ed