LCA length - how much of a difference would 1/4" make?

Knowing that my RE 3.5" lift is sitting considerably higher than advertised, I finally took a tape measure to it and found I'm sitting at 22" in the front and 21.5" in the rear (hub to edge of fender), meaning it netted approximately 4.5" of lift...

My LCAs are adjusted to 16.25" based on the handy chart tossed around as a reference, and as a result I think I need to lengthen the LCAs a bit more to achieve proper caster angle.

At this point, my XJ tracks straight but tends to be a bit on the twitchy side - it wanders a bit and the reactions to relatively mild steering inputs can be startling at highway speeds.

My UCAs are adjusted to stock length (15") - would lengthening the lowers by roughly 1/4" make a notable difference in this issue? I know it's difficult to say, but I'm hoping someone else has had to make a tweak like this at some point in the past.

that 1/4 inch would help it to not wander because it would correct your caster angle, that will cause the steering/wheels to want to return to center instead of wandering

Increasing the caster is always a good thing. It'll help your XJ track straight and increase the return-to-center of the steering. That being said, your pinion angle is just as important, if not more. I'd make sure the pinion angle is good (1 degree under parallel with the driveshaft I believe?) before anything else. It'll save u-joints in the future. If you lift a Jeep, you gotta know you're going to sacrifice a tad of driveability.

x2. pinion angle>caster. that being said, have the pinion low enough to have somewhat tolerable caster, but high enough to not get any vibes, even on acceleration.

Buy a $35 digital angle finder from sears and measure everything to get it within spec. Those charts, while handy, are just guidelines. Everyone's setup is different.