If someone were to attach a saddle to a predatory animal with a flexible spine how might it work and what would it be affixed with? Keep in mind medieval technology is the limit (although if it is feasible with their technology but not with their know-how I'll accept it.)
I suspect You may find of interest this Answer to a similar question (I'm unsure if I should mark this Question as a duplicate).
General idea is saddle depends on usage and relative size between mount and rider.
If You are using a predatory animal as mount I suppose you want to go to battle and thus you'll also want to use as much as possible you'r mount's offensive power.
This would mean you should move saddle front in order to weigh over shoulder blades with direct support of forelegs and have some kind of retention for rider legs to avoid disastrous falls when mount leaps or rises on hind legs to fight.
You also might need some effective way to prevent tendency of cats (if mount is a cat) to roll over in a fight.