ALL AT 75mm reloads are certified to fly in the corresponding length CTI hardware.
ALL CTI 75mm reloads are certified to fly in the corresponding length AT hardware.
It is advised to use the AT seal disk and o-ring in both combinations.
If you buy a 75mm AT reload, make sure it has the single-throat nozzle, AT recommends it in the CTI hardware.
I like using it anyway.
I fly at MDRA, so uncertified combinations are allowed as long as the RSO approves your flight.
I use a the above combinations plus I have used these loads in Kosdon/AMW hdw with the hubcap adapter.
You can use spacers for longer cases but again I have no proof their use is certified when mixing different manufacturers.