Hmm, you have a similar setup as I do. Blitz 99 cab, U360s, 7 buttons each, trackball, but mine is converted to a 4P control panel.
I have the GGG Hi-Lo Turbo Twist Spinner. It's awesome. But expensive. I love the Tron spinner knob that comes with it. It's a very well-balanced spinner. The optional steering wheel you can get with it makes it a nice choice.
My only gripe is the mounting plate. The mounting plate is small and designed for top-mounting (which is fine), but the screws are pretty close to the hole that the spinner sinks into. This seems a little structurally weak, but so far so good I guess.
And in my case, I have a plexi cover for my control panel. Unfortunately, drilling the holes for the screws cracked my plexi (partially because they were too near the sink hole for the spinner).
Regardless, I do recommend that spinner.

And I have mine mounted on the left- but I have a Tron trigger stick to the right of it, so I went for the classic Tron layout.