Not bad dude. Imagination drawing is hard. Might I recommend you look at Loomis' "Figure drawing for all it's worth" book? Really quite something, it is.
I think some studies from there, in addition to Posemaniacs will really help you draw the figure better.
Possibly practise some [posemaniac] dynamic pose drawing too if you like (doesn't have to be 30 secs, you can just try the regular pictures and go for a couple of minutes if you find it a bit too short)