C,
I can't see any reason not to use an in-ground SWCG for an above ground installation...
You can use the 25K T-9 model, but as PM says the 40K T-15 would be much better... The T-9 generates .7 lbs. of chlorine gas per day at 100%. The T-15 generates 1.4 lbs. of chlorine gas per day...
Most pools use 2 to 4 ppm of chlorine a day. With T-9 you will have to run your pump for 12.5 hours to generate 3 ppm of chlorine.. Not a problem with a VS pump, but much more costly with a single speed pump...
Thanks for posting,
Jim R.