I've tested my code with the TNC-Black from Coastal Chipworks and it works well. Weight isn't a huge issue on my flight; I'm focused on high altitude photography. It's just more fun for me to do things in software whenever possible. I'd really love to do the mod/de-mod in pure Go. There is an interesting example of a modem in Go but I have much more learning to do before I could write one of these for AFSK:

http://bemasher.github.io/rtlamr/

Awesome tracker, by the way! I'm super jealous of guys like you with actual engineering skills that can put together a custom integrated package on a PCB like that. Would you consider putting up your schematics and Eagle files on Github or similar?

Definitely! I have a couple issues I need to fix on the hardware so the board runs without mods, but I plan on posting all of the hardware/firmware very soon once I get that wrapped up.