Existing 14x14 center Vent prep for AC on 1961

[Studioman]

My idea of a 10k portable AC unit just isn't enough, I need a roof top ASAP!
My 1961 Ambassador is NOT prepared for nor ever had AC. I did run a new 12/2 wire to the pantry ready for a new Roof top if needed.
I also have a 1/2 tube ready for the drain (But mounted below the existing ceiling).

I was hoping to just put the AC unit on top of the existing center vent in my 28' Ambassador? Or do I have to cut this "lip" off? It would be weather-proof if I could leave the lip or leave at least part of it, and it would add to the structural support needed IMO.

How do I catch the water to put it into my new drain line?
Any assistance or pics on the best way to do this would be GREAT.
I bet I can figure out the drain, but I'd love some opinions on the pan/ frame issues.
(As the roof is round on top but the AC units are flat at the mounting surface).
Thanks in advance!

[Lumatic]

First I have not done it myself but did have a 13.5 Dometic Penguin installed on my Tradewind. I did have it installed by a pro. He added a 2x4 frame between inner and outer skiin to support the AC. The Penguin looks nice and streamlined on the roof and is reliable. If I had it to do over again I would pick the tallest AC I could find. Because the Penguin is low there is more noise in the coach. Also capacity of the AC is important for boon docking. It may be difficult to use a generator to power up a 15K unit.

[Studioman]

I HAVE to go with a low overhead unit as my tallest shop door is only 10' (9' 10 3/4" to be exact).
It's SO CLOSE!!! I have considered making a cardboard mockup of a normal unit (14" tall), as it saves the noise and cuts the cost in about 1/2 compared to a low-profile unit. But as I said, it's just SO CLOSE and I'm not leaving it outside when not in use.