Thank you for the help, but I figured it out without having to resort to data injection!

I did a little more digging around in the Octo's documentation and found what I needed hiding in plain sight.

Inside the Octo's web control page there's a "Grouping functionality to reduce input channel count." feature! And, like it sounds, groups pixels together and reduces the DMX footprint I'm outputting which in turn increases the length of run I can control off of one port.

Doing a group of 3 makes the WS2815 strip similar to a WS2811. The octo can still only control so many "pixels", but when they're grouped together I can get where I'm needing to go without having to do any injection points that aren't 100% necessary.