Aggh. I actually prefer the previous version over this one. I tried getting a bit too involved with it, I think - tried changing too much at once without checking each stage. Lesson learned.
I altered the height of the down, passing and up positions to try and smooth out the bounce and I think it looks better, but the legs, I feel, are much worse. I tried to sort out the leg's popping by altering the passing and up legs - it sort of worked, I think, but now the leg very suddenly comes to a stop on the contact pose when it should probably keep moving backwards. In retrospect I think I may be able to fix that by dropping the height of the contact pose slightly and moving his leg back a bit more but I'm concerned that will mess up the rest of the poses in some way.
I did also end up extending the front leg a little more on each contact pose and I'm not keen on the way it looks. I think the stride is a bit wide now. Sort of looks like he's marching!
I did try to do something a little funkier with the feet on the 'up' position as well by rotating the toes so they were flat on the floor and the heel was up, giving a bit more of a push, but due to the automated keyframes it sort of bumps up and down rather than sliding and moving smoothly. I'd probably have to alter each frame by hand to fix that, so I think I'll revert it and just leave it as it was. There'll be time to refine these things later. It's more important to get a solid block done at this point.
I'm actually wondering if it is at all possible to fix the leg popping using so few keyframes. It seems, again, like something you'd need to manually tweak or with the fcurves. I'll give it another shot but I might need to ask Jon for some advice on that one; I don't seem to be able to fix it no matter what I do!
I'll probably go back to version 4, which I feel was overall a little better, and make some slight height adjustments to that one to see if I can smooth out the bouncing. Then I'll look at tweaking the legs a little more.