I've tried a good almost half dozen harnesses on Shamas so far....I can attest that an ill-fitted front-clip harness negatively affects gait. I have noticed that Shamas has a tendency to go sort of "bent" along his spine when stopped from the front, if he forges ahead on an ill fitted harness. The best so far: Kurgo Journey. Still not the good fit I'm looking for, but we can't swing the $80+ shipping for the Perfect fit. The biggest thing I find on a front clip harness is that when the dog pulls, the harness shifts sideways.....and interferes with the leg movement on whichever side the lead is on. That seems to apply whether it's the Easywalk, which drags on the back of the leg joint, or the Kurgo, which contricts the front of the leg.
So far I've used Easy Walk, Step-in, Y-harness, H-Harness(the car-restraint type) and the Kurgo Journey. Harnesses are beter than collars for Shamas, because he's got a tendency to panic and bolt, or lunge.
I'm actually currently toying with the idea of a harness that clips off the shoulder. I like Shamas to walk on my right side and a local merchant has designed a harness that has the clips on the shoulders. So I put a Carabiner clip on the left side of his Petsmart Y harness, and I've been walking him with that the last couple of days. Less shifting, better gait, and a more relaxed walk. You can see it below, in the pic I took this morning. The biggest thing I find with Shamas and harnesses is that they tend to sit very close under his arm pits- doesn't matter what harnes I use. It's just the shape of is body. I can buy one that's long enough to sit further back, and it'll shift forward and sag in the front. :/
If you have a dog that lunges, then using the back clip leaves you with a dog leaping away from you while you try to pull it away. Not a good option either-it looks for all the world like your dog is getting away from you, and is very scary for the person on the receiving end! Front (and shoulder)clips let you turn the dog easily, getting his attention back on you so that you can continue with the walk.