How much load weight added to dry weight

Well, hello. I have been reading in the forums for awhile. I am not currently a TM owner, but hope to be one one day. A goal of mine is to travel the US in a TT. That trip is something that I've wanted to do since I was a teenager and read Travels with Charlie. Well, a lot of life has since passed; I'm no longer a kid but the dream lives on! When I do this trip, it will be 2 adults and a 42 pound Goldendoodle named Scooter in the TT.

I have a smaller SUV, which has a tow limit of 3500 pounds. Because of the 3500# limit, I am only looking at the 2619 or any of the 2720 models. My question is what is a practical weight to allocate for all of the miscellaneous stuff that one needs when using the TM for the big trip? Also, I am interested in the solar panels and want to know how much weight they add.

I do know what water and propane weigh and if I add them to the dry weight of the TM models that I'm considering, I come up with remaining load capacity of 621 (2619), 552 (2720), or 429 (2720 SL/SD) pounds.

Anyhow, thanks for your thoughts and I really enjoy reading the forums - I have learned so much and none of it has scared me off!

Pat