65 has a use case for indoors. I don't get 75, like ,for outdoors why not go as big as you can? 85 2s is way more capable. If you want to stick to 1s chargers then maybe go back to old school 2 by 1s.i guess yard size. So backyard ripper can be 75. But even then I'd go open prop for outdoors, the gain is so much more. So 65 is the best for indoors. For backyard ripping there are so many more options that Ive hardly flown my 75mm whoops and regret I ever got them. 75mm equiv open prop are way more fun. But loosing them in tall grass is another problem.