So, let's start with canine/feline typed legs. These animals are built for running, and those huge thighed back legs are made for strong thrusting off the ground during the chase, and leaps and assorted carnivorous activities like that. More of the animal's weight is centered on their front legs, the hind legs are mostly for power. If you want to make a feral styled suit, by all means just tack these onto your suit/character's design, but they are inappropriate as-is for an anthro/bipedal design. Nothing irritates me more about character design than seeing an anthro with 'stock' digitigrade legs just tacked on (except flat footbottoms).

I make my characters, and my designs, based off of the concept of divergent evolution. Tl;dr, take whatever species your character is originally, and assume they took the same evolutionary steps that humans did to become something more advanced than apes. This ESPECIALLY applies to characters with anthro styled hands. Fen is considered to be a rather early step in this process, but a lot of the characters I work with are farther along in the anatomical evolution.

What does this have to do with the shape of digitigrade legs? If we assume that your character is on a similar evolutionary path to humans, we have to assume that the leg/knee structure will be evolving in a similar way too. Simply put, in order to bear weight and be functional and have enough stamina to viably survive, the hind legs will have to widen at least in the thigh area, and the foot will at least have to be bigger, if not longer too. The leg would also straighten significantly, because it requires less energy to balance a straight and locked leg than a bent one. Try it. These little things make the character more believable, because who wants to be a non-viable life form, eh?