I've been wondering the same thing myself. I've got a fairly soft fork right now (Manitou Axel Comp). Even on the largest drops I've taken (2'), I've only managed to use about 3" of the 4" available to me. This is in the softest setting. How much travel were you using when you tried out the 100mm forks? You probably don't want to cut it too close, but if you're only using 60mm on the average ride, you'd probably be ok. Closely monotoring your travel usage should be insightful in determining the right fork for your needs. I'd be curious what the experts have to say on this, as I'm just speculating.