The problem with the normal Cardan-type U joint is its tendency to lock up at certain points in its rotation due to changes in angular velocity if it's flexed too far from a straight-line situation. Using a double-Cardan joint with two crosses with a center link between them solves the angular velocity problem, but it requires a pillow block support to be installed on both sides of the joint for stability purposes. That's not difficult to do assuming there's enough space available. The double-D collapsible shaft is always a good idea!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!