I welded a bucket for my neighbours rear end loader, which he got for a bottle of booz, yesterday. It came with a bent and rotten muck fork, but he has more use for a bucket.
His model was a fixed one, not very practical as the weight is shifted way behind his Kioti CK20 but the lift height is still limited: when he uses his hydraulic top link, he'd pull the top link against the fuel tank behind the seat and still have only 5 to 6 feet of lift.
Next to the fixed type i worked on yesterday, there are two more common types in Holland:
http://www.wifo.nl/images/Bak balk.jpg
If you make one, the upper type is the easiest, requiring no external spools: You dont use a top link at all, but attach the boom to the top link bracket on the tractor. On the lower link arms, a yoke is attached that pivots on the main boom and pushes it up, thereby creating enough lift height to load a hobby sized manure spreader.
The other type requires an external spool, and shifts the weight of the load even further back and is just awkward in confined spaces.
I am also thinking of flipping the diff in a 50hp 2wd and installing my front loader over the rear axle. havent made up my mind yet.