7-channel panning

really depends on the setup. circle? one dimensional? irregular? dynamic postioning?

It's one-dimensional. it looks a little bit like this:

---1--2 --3----
4-------------7
5 ------------6

Ultimately, though, I'm not sure why/if I can use a patch like the one attached...and just have the 7th track start to blend back into the first?

your patch would be perfectly working when your speaker setup would be circular and everything had the same distance.

rectangles are more difficult and rectangles with irregular distances between the speakers would normally require some more math.

is there a specific reason why you dont arrange the speakers with equal distribution? or why you dont use 8 ?

or at least arrange stuff in a circle shape, then the "missing" speaker at 180 degrees is ok. a circular setup will be much easier to control as the weighting between neighbour channels is always the same, no matter hor far the distance. :)

it's not really my set-up, so i'm unable to alter it too much..
there are only 7 speakers there, the speakers are pretty firmly mounted into their respective locations..

is there a way to evenly distribute over 7?

From your diagram it looks (somewhat) like a 7.1 configuration - without the .1. With that said, a relatively straightforward way to do what you want is to use the ICST Ambisonic toolkit ( https://www.zhdk.ch/index.php?id=icst_ambisonicsexternals ) which has a downloadable package of max externals and help files, etc.. With ambisonics (and that toolkit) you can decode to pretty much any speaker configuration - such as the one you are going to use.

to do it for 7 wont differ from 8 at all when you use the technology of that patcher you got.

but the problem remains that the rear speakers are not as close to each other as the others, and that the arrangement is not a circle.

if you have access to the speakers while programming you should be able to easily adjust the gains for the channels a bit until you like the result.

try it with my approach in the attachement which is more or less based on a single expression, expr pow(((cos(($f1+$f2)*0.017455)*0.5)+0.5)\,(($f3*99.99)+0.01)) which allows you to set up the angle in degree and which also has a "broadness" parameter input.

Thanks, everyone.

Is there a specific approach in the amibisonic toolkit that is configured for 7.1 or is the point to just eyeball it?

I think this stuff is way over my head, straight out of the box..

I often use the [nodes] object to do sound placement with a multi speaker setup and simple panning. Here's an example I use for 6 speakers in a circle, but no reason you couldn't set it up for your setup.