UDS / Mini gauge steel questions and more?

I plan on making a UDS build and a MUDs build.
I'm trying to order directly from a factory that will provide me with new drums.

Question #1
I think I might be able to customize the thickness gauge of steel without a big price penalty.

For the 55 gallon drum they say:
Steel thicknesses range from 0.9mm to 1.2mm(can be customized).

For the 60L drum, they say:
Steel thicknesses range from 0.5mm to 0.8mm(can be customized).

Should I ask for a specific thickness for each of the drums?

Does it matter?

Question #2: I'm trying to make a MUD's and I'm wondering what the best option is for size. I've thought that the 60L would do but I'm not entirely sure. Here is the chart they give.

1 20L Open-Head Steel Pail 0.5~0.8 Ø326±3 285±5 0.5~0.8 Ø280±3 420±5

2 30(35)L Open-Head Steel Pail 0.5~0.8 Ø330±3 440±5

3 50L Open-Head Steel Pail 0.5~0.8 Ø380±3 450±5

4 55L Open-Head Steel Pail 0.5~0.8 Ø380±3 560±5

5 60L Open-Head Steel Pail 0.5~0.8 Ø380±3 600±5

6 70L Open-Head Steel Pail 0.5~0.8 Ø380±3 645±5

7 85L Open-Head Steel Pail 0.5~0.8 Ø435±3 600±5

8 100L Open-Head Steel Pail 0.5~0.8 Ø435±3 820±5

9 120L Open-Head Steel Pail 0.5~0.8 Ø435±3 830±5

Should I go for the 60 L or is there a better option for a MUDS?

(I've got a 12.4 inch Smokey Joe. It'd be cool if I could use the dome top for my MUDS)

Thanks in advance

PS - Is an ISO drum superior for a UDS build in some way?

Would you say that I shouldn't bother doing a UDS build unless I can get a drum with a thickness of 1.5mm or greater? I will only ever use the smoker in summer time temperatures if that is a factor. This is the only drum manufacturer I've been able to find in the country I live so I may be out of luck finding heavier gauge steel drums here.

Thanks for the advice.

Is there a size (among the chart in my first post) that might be appropriate for a Mini UDS?

And, while I'm at it, a size for a bcf engine?

Also, should I get a bolt lock ring or a lever lock ring for my 55 gallon drum?