Yes, the Adco Olefin RV Cover part # AD97ZR that you referenced is the correct size for your Starcraft TravelStar 21SB and is the best option overall. It offers the best protection in all climates and is also the easiest to install as well so we recommend it highly for you!
I attached an install video for the cover for you to check out as well. view full answer...
A good rule of thumb would be 1 solar panel for 100 amp hours (ah) of battery. The larger your battery bank, the longer you will be able to use your equipment. The amount of solar panels will just dictate how long it will take to restore the batteries back to fully charged.
More than likely a good size would be (2) 100 ah batteries with a 2 solar panel kit like the Go Power Solar Elite Charging System # 34282184.
But, I have also linked a solar calculator. Using this solar calculator,... view full answer...
For your 7,500 pound camper with a tongue weight of 500 pounds, the 500 pounds is most likely the dry weight. With that being said, you most likely have a loaded tongue weight of around 750 - 1,000 pounds. This weight is important to determine the correct firmness of the setup.
With that factor in mind, I recommend the Fastway e2 Weight Distribution w/ 2-Point Sway Control - Round - 10,000 lbs GTW, 1,000 lbs TW # FA94-00-1000. The e2 comes with side-to-side sway control to dramatically... view full answer...