Its mostly measure/ponder/measure/ponder. You do need it balanced after or you will have some sort of vibes.
Getting more slip yoke engagement will probably reduce the vibes a tad, but you can't go too far or it runs out of space to slip when the rearend moves or the pinion rises under throttle. Then you shatter the bearing seat in the rear output housing of the tcase, like I did once. Mine was due to tons of throttle, rocks, and no bumpstops in the back, but a too long driveshaft will do the same thing.
An SYE is the ideal fix, but if you don't mind a little vibration, just get used to replacing 9 dollar ujoints and make sure you aren't maxing out the angle on the ujoints. Torsional vibes will wear the drivetrain parts a bit faster but I have been living with them in my MJ for years now*.
when you go to longarms and 6", I would recommend it though. A traction bar might be a wise choice too.
* really extreme vibes (like, doing 103mph with the pedal on the floor for hours with a driveshaft with the ujoint yokes welded in 70 degrees out of phase and never balanced at all, felt like driving a massage chair) WILL do damage. I found small stress cracks in all the stiffening webs in the tailhousing/4x4 adapter housing of my transmission after that stunt. It is my spare now, so I hope to learn to TIG and grind/fill them all before I rebuild it sometime in the next year.
