This was on a truck that had 6" lift blocks on the back, even after I told him that 4" was the most you can go with the 1-piece without using a spacer. 6" usually requires a spacer (if it's a true 6 and not 6 in the front, 4 in the rear) and 8" lifts always require a spacer.
The truck had 22. 5" wheels w/ 37" g-rated tires on it and he was running it on the track.
I saw him run the truck before and he had HORRIBLE axle wrap because of those enormous lift blccks in the back. The axle wasn't only wrapping, but it was also dog tracking, because he had an open diff. You could VISIBLY see the driver side rear wheel move forward when the truck launched.
Combine that with a bigger turbo, bigger sticks, Smarty and he simply bound the u-joint and he snapped the yoke.
He is now on his third shaft. He broke the OEM steel one, then he broke the aluminum one, now he's FINALLY listened and lost the lift blocks and added a set of traction bars.
This is THE only shaft I've had come in broken. He also broke the transfer case right after this by driving the truck around with no rear driveshaft and using the truck in 4WD with only the front shaft.
I'll tell you flat out if I think something isn't going to work or isn't going to work right. It may cost a sale and you may not be very happy about it, but if I think it's going to damage your truck, I'm going to tell you.
Broken trucks and "close enough" is not a good way to do business. It might work when you're working on your own truck, but when my name is on it, it's going to be right. It might take longer, but I refuse to do half azz.
There are things you do to get you home and there are things you do to make it right.
Folks make a much bigger deal out of the u-joints than there really is. The 1-piece goes through joints less than half as often as the 2-piece shaft does. The main factors in it are 1 - You don't have a center carrier bearing to induce vibration and 2 - the operating angle on the joints is half of what it is on the 2-piece and the joints are closer to being in phase.
By putting in the wrong joints or not having them sized correctly, you'll do one of two things. Either you'll have the joint too tight and it'll bind or you'll have it too loose and it'll vibrate. My personal opinion is to use the joints that were intended for the application UNLESS you have the means to accurately machine the caps or the circlips (which does work fine, it's just not our preferred method). I'm sorry, but an angle grinder on a driveline component IS NOT the way to do it.