Robert V, the 1500 series is excellent for rotary processing and in my experience doesn't give any unevenness in developing.
I have processed over 5,000 35mm rolls of film in the 1500 series of tanks, I cannot ever remember having uneven development. I'm sure if I did have uneven development I would have that particular roll of film hanging up in my darkroom!
The 1520 tank, coupled with the 1530 extension module, is designed to hold 5 rolls of 35 mm film. The same combination without the reels and with different stickers on the outside, is the 8x10" paper drum.
Using my own 1520 tank and 1530 extension module, I have developed 35mm film, 120 film, colour paper, B&W paper, 8x10" sheet film (Colour negative, colour transparency & B&W) and Duratrans. These are the things I can recall off the top of my head.
The 1520 tank actually holds 2 x 35mm reels, you may be getting confused with the 1510 tank which, as it's name implies, holds 1 reel.
It is my understanding that the 1500 series of tanks and extension modules was designed from the ground up as a rotary processing system, with the added bonus of being able to do inversion processing with a small change; requiring either the addition of a magnet, or the lid cog.
I have been running my own Jobo system for over a ¼ of a century, prior to that I was using Jobo in a couple of labs, which is where I found out about it's incredible versatility.
Dan, you have made what could possibly be your first investment in a huge system. Look carefully, and, if you are lucky, you may find some extremely versatile additions to your basic system.
I have actually had uneven development with the larger 2500 series of tanks, I was processing 4x5" sheet film last year when I had this occur. It was unrelated to the actual tanks, being the 2509 reel with six sheets on, not too good.
Mick.