Realizing that later quest packs sometimes modify the original rules intent, but still seeking something official... this is from the Elf Quest Pack (page 3 on phoenix's version):
Long Pit Trap
If a Hero wants to jump over this pit the long way, he must have at least 3 squares of movement left after he moves next to the pit. The Hero then rolls 1 Combat Die. A Black Shield means the Hero has jumped across safely, using up 3 squares of movement. The Hero can continue to move if he has more movement left. Any result other than a Black Shield means the Hero falls into the pit suffering 2 Body Points of damage. The Hero must roll a 5 or 6 on 1d6 on a subsequent turn to climb out of the pit. While in the pit, the Hero rolls 1 less Combat Die when attacking or defending (but never less than 1 die).
Note: These traps can be jumped the short way, the same as regular pit traps.
If using the Rabbit Boots, would I give them a bonus? You bet I would...
But if you still wanted to make it a challenge, I guess you could make it that they have to roll anything but a skull instead of anything but a black shield, but that's just a suggestion or just let them have it.
And
Against the Ogre Horde makes it clear that Pits of Darkness can't be disarmed after being sprung, but are jumped like normal Pit Traps, if that's any help.
Now the "earthquake tile" in
Wizards of Morcar is said to be treated like a Pit, but it doesn't mention the crazy stunt of trying to leap over it the long way, I'm going to assume you just can't do it even with the Rabbit Boots!