3 ACs is never a problem on 50 amp. 50 amp each leg, not total. 2 ACs on one leg, 1 on the other. Each drawing around 16 amps average. Depends on unit, if it has a hard start capacitor etc. Motorhomes do it all the time. At least most of your 38-40' pushers do.
Our last fifth wheel was 40' (4 slides) with 2 - 15k AC's. It only would maintain temps after several modifications. 36' class A (4 slides) we had had 2 - 15k units and a darker full body paint. It would not keep up at all unless you had shade and cooler temps. That said though, I'd never own another rig that big without 3 ACs. Always better to have too much than just enough. Plan on one going out in the middle of the summer. Always possible, then at least you have 2 backups instead of 1.
On the shower, I've had to remove almost every shower door we've owned due to leaking, including the latest Jay Flight. I pulled the whole thing, then laid a thick bead of silicone under the track, set it, then sealed inner and outer as well. Similar on vertical end pieces. Never had a problem doing it that way.
John and Rebecca Dickson
Emma-8 / Little John-5 / Iva-1+
2013 Ford F-350 Lariat FX4, CC LB PSD, DRW
2015 Jayco Jay Flight 28BHBE (#8)