Hi,
I'm from Italy and i'm the proud owner of Nero, a 14h Italian 
ack mule, as you may remember from the older (now gone) thread, i was used to horses and was clueless about the differences between horses and mules and had some troubles with him at first, but then we became good friends and now he's really willing and enjoyable to ride
Mules are still very popular as pack animals in Italy but hardly anyone considers them as riding animals here, so it's extremely difficult to find suitable riding saddles and tack here.
also, since they're not bred for riding, Italian mules, like Nero, are small, mutton withered, short backed animals with a rather stocky build, so most saddle meant to fit the typically larger and horse-like American mule are simply too large for our mules, so by now, i'm riding him bareback (luckily he has a rather round, fat, comfortable back)
I'm in contact with a saddlemaker to have a custom western saddle built for him, but it's nothing easy, being a small short backed mule he won't take any tree with bars longer than 20" but on the other hand i'm a stout 200 lbs man and i can't ride in a seat shorter than 15".
The only way to build such a tree is to make it with very little or almost no bars sticking out behind the cantle, is this an acceptable compromise?
Here are some pictures of Nero