Here's an idea: put a zip tie or something on the metal shaft of each shock, then find a hill or loading dock or something to flex 'er out, until the opposite wheel is airborne... then see where your zip tie is. That should at least give you a rough idea of available shock travel, maybe have a buddy watch who can yell at you if you start to bottom out a shock.
There are really only a couple things that will limit your travel- your springs will stop flexing (and there's not enough weight to get them to arch further) or something smacks into something- like a tire on the fender, or axle on a bump stop, tie rod on a driveshaft, shock fully compressed, etc. find out what's limiting your travel, then worry if you need to limit it further.
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 01 XT225, 09 TTR125, 07 TTR90, 07 CRF50