Driveshaft question: usable travel in slipyoke

Ok,basic question. What is the minimum/safe travel i need in a drive shaft slipyoke.
What im trying to do is use a front driveline the for a rear. I just installed an AA sye, and a rear D44. Distance from yoke to yoke is 32 3/4" roughly. My front shaft is 33 1/2" extended,30 5/8" collapsed. From the driveline faq sheet thats the longest factory front. Is it possible to use a zj driveline?
Just replaced every suspension part on it,trying to use the last 300 on shocks instead of a new driveline just so i can get it wheeling again thanks in advance
2000 xj,auto,4.5",d44,hp30,zips and 4.56s.
Thanks

just remember that when your rear suspension droops, your driveshaft will get shorter as the axles moves forwards. i would see how far your axle drops, measure yoke to yoke then load the rear as much as possible to squat the rear and then measure yoke to yoke.

I killed my stock front shaft trying to run it in the rear. Worked for a while but in the end it was too short and wore out the slip in a couple of months. 2000 AW4 231 SYE.
I had to have a shaft lengthened in the end. But I did have a few ZJ shafts shortened to work as it was a cheap interim. But they are fairly small tube, and was concerned about durability. Still keep them as trail spares though.