you can flex all day long, the pumpkin will still be relatively in the same spot as it is when you are just sitting there, each wheel will travel, but the center of the axle will pretty much stay put, unless you jump it or bounce really hard.
just take it easy and i'm more than sure you will be fine. let er flex.
i bought a sye a few years ago, it's still in the box on the shelf. i'm running a stock length drive shaft with no t-case drop. all i have done to my shaft is a yj slip yoke for the added clearance so she won't bind.
my plan is to mate my d300 up to my 231, so i'll use my sye on another jeep.
1990 xj 8 inch Staang's Fab long arms
1999 xj. current daily driver
2000 xj 4.5 inch rubicon express, 33 timberlines
1997 tj 2 inch bb, 33 mtr, trailhead customs tube fenders, titan 10k winch
1999 tj 2 inch bb, 2 inch bl, 33 mtr
I get mine from TMR Customs