Update on the previous walk cycle. It's still messy and lacking in consistent volume but I've added most of the inbetweens at this point. I tried to animate intuitively rather than mechanically, adding inbetweens where I felt they needed to go rather than placing them formulaically where they should go. I'm not entirely satisfied yet — the arm in front lags a bit when it comes forward, so I need to have another look at that.
I think the previous jerkiness was caused by the up position rather than frames being misaligned (though that was certainly a factor). He kind of lurches forward too far and sticks his neck out which causes a bit of a jump. I redrew it slightly so his body was straighter and his head and neck were less stretched. It looks a bit better now but there's still a bit of a jerk in there but I can't figure out what's causing it. Hopefully coming back to it with fresh eyes after some sleep will help!
Once I've got the movement as fluid as I can I'll work on cleaning up the lines and fixing the problems with volumes.