Just a couple of thoughts.
IF you can safely set up a small video (eg a gopro) that can film the panel / altimeter, start it, film the GPS time, then let it run. That way you can sync the two up. Just a variation on the theme of photographing the GPS time so you can geotag photos after the fact. There are also some GPS's (e.g my cycle one) that have baro altitude.)
The other thought is that you don't seem to have a way of considering positioning. I'm not sure it is feasible, but for example e.g. if method 1) makes the turn in 300ft, but leaves you 1/2 a mile further away than method 2), which takes 400ft, which is favoured?
Otherwise, I look forward to the results. In retrospect, I think the my approach probably isn't/wasn't representative, as it pre-supposes you're making the turn.