My JD is 8.5” and hes only 1 year old and gonna get bigger. If a male JD doesnt grow over 8” its due to poor diet and living conditions. I have my 8.5” male JD, 8.5” male texas, 8” male jag and 6” male jag in a 6’ 150 gallon tank and I feel like its to small. I have an 85 gallon tank and I would never try to cram my JD, Texas and jag into that at the size they are now let alone as full size adults. Yes they will physically fit in the 75 but they wont be happy and already aggressive fish will be even more aggressive and you will be doing large water changes frequently if you plan on trying to give them decent water conditions to live in. IMHO I wouldnt even try it unless the plan was to grow them to 4” or 5” and move them to a suitable tank.