Here is the XXL UDS I built a couple of years ago. This is a two door model. Yes it is a pain in the arse to seal the doors! I used red RTV on both top and bottom. I need to run another bead to get the nooks and cranys yet. I have used this with a water pan and without, it is just personal preference.
Can it be done? I say yes, however, you are gonna need a donor barrel. Instead of pics here I found the thread from when I built it.
In a regular barrel, it has been rare I have ever needed to add fuel so I doubt I would do a door.