Backstory: the way I did this was to edit an unknown alien stat in the executable to an easily recognizable number (100 is good, but something like 101 is even better as it doesn't show up very often), then see if any offsets in UNITREF.DAT matched.
Why didn't some edits show up in UNITREF.DAT though? Well, the game ignores these values and does not transfer them to UNITREF.DAT (another option is that a value outside of the expected range is either ignored or reverts to the first value in the range - doubtful, but sounds good). Why does the game ignore some alien stats in the executable? Well, most are due to the fact that a stat was dropped during development or was never implemented completely. Back when I first started this topic I had a strong feeling that all alien stats in the executable were used somewhere and as I know now, this is just not the case. The game was mostly complete, true, but there were things which never made it in for whatever reasons.
We've made great progress over the years deciphering UNITREF.DAT and for the most part it's completely understood now. For this reason, I've updated my Alien Stats page on the site to take this info into consideration. Most of the changes can be found under the Editing Alien Stats heading. It's really a good feeling to see a section fully fleshed out after years of nothing but question marks. No more unknowns!
The one thing I want to do to the page yet is put descriptive anchors instead of the junk /#ufostatsX. Shouldn't be too hard to fix that.
Anyhow, I figured I'd keep everyone updated on this!