If I played euph regularly (and played regular euph parts instead of other stuff I do with it), I'd probably use the 104 rim. I had one for some time, but discovered that I never used it. I might also use a slightly smaller cup. But I find the J/J9/106 setup to be a good all-around solution for me. And you can get Lexan rims from Doug without difficulty.
I would have saved a lot of money over the years just buying from Doug. But I wouldn't have learned as much.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)