Yes, the GV uses a Kick Driveshaft, where the XL uses a 2-pc driveshaft with a center bearing and a 3-bolt flanged CV at the pinion.  Figured I'd spice up this thread.
As for my break,  Unspectacular to say the least.  At Paragon on Rattler, all  weight was on the driver's rear, a little hopping and BANG!.  The carrier cap got a little deformed from me driving on it for several miles to get out of the park.
Thank god for the ARB.  Man, do they use good steel.  If that was a Kick carrier, it would have shattered just like they have in my biddies rigs.
Spidertrax is in the process of making up custom molt shafts for a buddy on the Yahoo GV list.  They will use all the stock 4-channel ABS stuff, but will be splined for the 27-spline Dana sidegear.  They will require you to use the ARB diff with Dana sidegears installed into it.  That should make for a strong axle.
Yah, I'm on the yahoo list. Haven't been watching that list for a while. Seems a lot of people there are still 'beginners' for the off-road community, if they want to do that in the first place. I do recall 'Kelly' IIRC that he broke his rear axle. I thought he was back on the road.
Last month, Godzookie wrote an article about using a Calmini's Anvil, XL7 housing, 5.83 gears, Easy Locker, Sami carrier to go into his Sidekick.
So basically, I can upgrade the the X's front axle in the same meaner. Then to match the rear, look at your suggestion. This will provide an increase in gear ratio for the larger tires.
Would you happen to know if Spidertrax is looking at making the GV axle a full-floater? This would support the higher carrying capacity of the X.