They are some old ass boots, that have been modified, so maybe the 100 flex guess is inaccurate. I somehow ended up with 3 pairs of them, so I've been in the same model of shell for almost 15 years. Wear one out, rotate in the next pair. They are green translucent Salomon 1080s, listed as an 85 flex. Figured +10 or so with the Intuitions.

At room temp they flex about the same as the Lange XC 120s, stiffer than Lange XC 100s, and a lot stiffer than Full Tilt 8s. The Salomons don't seem to change much with temperature, but the Langes sure do.

Thanks for the advice. I'm thinking I'll give the 120s a go.