question on front DS in rear

So I finally got my jeep all back together after too many bumps in the road. I did a RE hack n tap (242tc) and have a front shaft in the rear. I have ample room left in the slip joint in either direction, but just had a question regarding that. I havent really driven it much yet or been able to go out and flex and drive on any rough terrain, just wondering how much the shaft actually will extend/shorten at the slip joint. From just jacking the jeep up to put on stands and compressing the suspension it doesnt seem to change lengths at least not enough to be obviously noticable. Just wondering how much play there should be going in either direction on the exposed part of the shaft. TIA!

Use geometry.

The DS is the hypoteneuse, upward travel of the axle is your y component and the x component stays constant (distance from joint on output shaft to point directly above axle).

Say your X distance is 26 inches (rought estimate) and your vertical y travel (from settled to dropped) is 4 inches. And the distance of your settled axle to the point above it (straight back from the output shaft) is 5 inches. The change in hypoteneuse length here will be:

(26^2 + 9^2)^(1/2) - (26^2 + 5^2)^(1/2) = 1.0376 inches

so therefore, even if you get your differential to travel 4 full inches, the DS length will only extend about 1 inch.