If you get your hands on the 1/12 kit you could use that for a pretty decent reference. Then make the parts you want scaled up from that.
Also, take some time to look closely at other 1/6 scale F-16 models and take note of the items you can actually see once the pilot is installed and canopy closed. That's where you want to spend your effort. No point building a highly detailed cockpit if you can't see all of it. If your canopy will open then perhaps you will see more detail etc.

Btw, I'm in the same boat as you as I'll be looking to start an Avonds F-16 this winter. For that scale (1:6.8) there is no commercially available unit so it will need to be scratch built.