I'll tell you another reason you might like 900.
If you can get an outside site from about 1/3 of the way around to 2/3 of the way around, those sites back up to a "dog walk" area which is a LONG (and sometimes wide) shaded open area that runs all the way from behind 900 down behind 800 and it funnels down to the other end of the dog walk entrance which is about 3 sites into the 700 loop. There is a sign (or used to be) just off the bridge between the 900 loop and the Creekside Meadow group campsite across the ditch. Anyway it's would be good for the dogs (close by and it's still leash on) but I used it as a short-cut to get down to the MK boat or Pioneer Hall when I was in 900. You can still use the dog park when you want to go leash off.
Rather than walk from the back of 900 out to the main road then down the sidewalk, I just went off the back of my site, hung a right, and came out into 700 (you cross the old wooden FWRR ties just before you hit the pavement). I think there is a dog walk sign down at that end too. Then hang a left and go down through the 700 loop on its road and come out down by PH. Rode my bike down through there too fast and easy.
Nearly all the Premium sites should handle your rig. And given how long you'll be at the Fort, it might be worth it to move midway through your stay to experience another loop. Would take some work but it might prove interesting.
Bama Ed