I wore some shorts underneath, the Equinox is rather hilly, and I didn't want to get into any trouble... However, at home on the treadmill... No issues discovered either way, but certainly preempt chaffing the usual ways (petroleum jelly, or better yet, find some good silicon based stuff like Bodyglide or the Mission brand anti-friction cream, its much more resistant to sweat than the petroleum based stuff).

I love those VFF's! Due to the rocky terrain, and roots, I had to switch from KSO's to the KSO Trek Sport model for the thicker sole on the bottom...