Welcome to the forum! I just did my first 120G propane tank RF build, took me 5 weeks to complete it.
Door cuts seem to be the most problematic issue for people, luckily, I did not run into this issue.
I cut my door in stages to prevent warp. I used a thin cut wheel on a grinder, cut the proposed sections
where the hinges went, then moved around the tank, only cutting about a minute per cut, moving to the
opposite end of the tank and back, until the cuts were complete. Same for my initial burn, I only had
very minimal warp on one corner, maybe 1/4" on one corner, I just heated it and pulled it back.
Once a whole door is warped, I have seen people use chains to hold the edges and use a bottle jack
or floor jack to put pressure in the arch of the bend and force the edges back into where it should be.
Do a search on "warp" and you should find some of the posts.
I went through the same dilemma of round vs box. I ended up building a square box out of 1/4 plate.
To me, the matching up of the 2 parts was easier, though some may say differently. If I was to go the
round FB path, I would have cut off the end and capped it with flat plate to make the mating easier. Same
for equipping the box with a door and a fire grate, seemed like an easier task to work with square components.
Good luck with your build!
