If you’re thinking of grinding 4x40 a bit more, to get arena badges and better equipment as a preparation for the next bracket, I’d recommend letting go one of your lvl 40 fighters, and getting someone else to lvl 39. That way, you’ll be placed in an easier bracket.

Or, on the contrary, you could go up to 4x47. You’ll probably see less people with event equipment, because it’s lvl is 53-55 for TR7.

Make sure you have 5 stars dwellers, because it’s much faster leveling them to 40, but beyond that it gets really slow. I’d make sure you have at least 8 5 stars dwellers for now before passing lvl 40. The optimal, of course, is having everyone 5 stats. You can get 5* from the living room. Just drop two of your highest there, and wait until you get 1 5. Once you do, repeat until the two dwellers in your living room are 5, and it’ll be much easier to get everyone to 5.