Ended up buying a used Tepui Gran Sabana (aka Autana XL) from my cousin. I followed the instructions
here to build an inexpensive unistrut rack. I used half channel strut as I wanted it a little bit lower.
To answer my own questions, this is one of the biggest tents sold and it fits just fine. I haven’t noticed a big change in COG, even in tippy situations. With MPG, I have a good baseline because I drove almost the exact same route earlier this year. I averaged .2 mpg less this time around but I also had more gear and people this time. I felt fine with my two year old in the tent. He obviously wanted to climb in and out by himself but we told him we had to help.
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We took a trip down to the San Rafael Swell to test it out for a night. For reference, it was 2 adults, a toddler and a 6 month old. We had plenty of room and the tent stayed nice and warm in temps down to the mid 30's.
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