Something like this might be a good start:
gamerule
engagerotation 90
engageheight 100 # or whatever; just higher than the ground
body l_leg
sides 0.130000 0.300000 0.000000
pos 1.200000 1.000000 0.500000
body r_foot
sides 0.200000 0.500000 0.080000
alt_sides 2 1 15
friction 5
body l_foot
sides 2 0.500000 0.080000
pos 0.8 0.900000 0.0
mass
joint r_ankle
radius 0.110000
joint l_ankle
radius 0.110000
pos 1.200000 1.050000 0.15
axis 0 0 1
range 0.5 -0.5
strength 6
I upped the right foot friction so it would stick to the board better. I'm not sure if the range and strength make much sense. As I said, it's a start, do with it what you wish, or don't.