I had a long chat with Winnebago service. I got a guy who knew answers. The MH is equipped with two floor vents that have shut offs. He is sending me a third. What he told me is that the system will be fine if I totally shut off two vents. If I do anything with the third vent, he said it was okay to totally block off 1 vent totally and that I should just shut off the other two partially. So I already know that if I shut off the hall vent, the air flow to the two front vents increases noticeably. One problem solved.
I learned that the floor ducts are encased in Styrofoam so they are totally inaccessible. He did say that the schematics I want are available on their site but that windows 10 would not work with them. The fix for me is that he is emailing me the schematics....problem solved.
I intend to open every compartment and crawl under the bus until I find the furnace, water heater and anything else I want to see.
We've made the jump from a 30 year old 43 foot boat to a 2016 Winnie and let me tell you, the technology change is overwhelming.
The tech also told me which outlets were run on the inverter and the ones that weren't. The receptacle closest to the front of the bus is safe to plug a 1500 watt heater into and that's the one we need to use. I can supplement heat with the portable and set the gas furnace to a lower temp and save gas. Winnie tech support has been very helpful.