Hello Thompson,
To be honest i dont mind modifying Tower 900 to fit rad. Im engineer and i have access to all tools i can imagine on work. The back of Tower 900 looks like huge space and i can desight bracket to hold weight of radiator. My biggest reason why i want to place rad inside is that i have cats. And we all know how big daredevils are they, she keeps putting her paws into ventilators on top of radiator, and not to talk about amount of hair Maine #### has.
Regarding Tower 900, my only issue is amount of airflow in front part of case where main component are, to be more precise heat output of 3090. From all pictures ive seen, case has only one fan on top of the case. And thats not remotely close to what i need.
P8 you suggested is out of question because of cat hair xD that wont work for me. Or any open case, for same reason i turned down Coolermaster Masterframe 700.
71 Case should be able to fit it if i completely remove HDD brackets and try somehow to squeeze pump/res inside since 3090 is huge. But issue is that later this year when i get front and back active plates for GPU and watercool it as well, so additional radiator/s are in plan.
So looking at current market, i have two options, wait till i get full watercooling system for GPU and then modify Tower900 to fit rads inside, or design my own case. Its possible and will take time, but id never mannage to get it done quickly or make look premium like one of your products. sandblasting/ cutting/bending/painting. So at this point i think ill wait bor black friday and hope i wont need to spend 1000€ for GPU cooling loop