I vote for going to Transynd in that transmission as well. We went to Dexron VI in our old GM 4L80e when Dextron III was spec.
In MH's we seldom 'wear out' but age out transmission fluid in my view. Going with the best fluid option is more preventive in my view. We got stuck once (cut short getting back in our own driveway and swung the right rear wheel with the tail just tagging the drive way just 6" out of the road) and was glad we had the better fluid. After a lot of work making a ramp out of large limestone rocks we backed it out but had to go to WOT to get it to lift out in reverse. I was afraid something was going to twist or break but seeing the ATF temps starting to rise I decided to go to WOT. With gravity working for us it came out but it was very hard on my nerves after two hours of hard work building the ramp.
If one gets stuck in stop and go traffic (especially up long grades) the ability to handle higher ATF temps is a plus in my view.