S.P.E.E.D.E.R. (Straddling Pilot Echoing Equine Disposition Ergo Rider)
Here's a sample recipe to make a more realistically proportioned human rider figure that can straddle a sci-fi/fantasy speeder bike or motorcycle:
S.P.E.E.D.E.R. (Straddling Pilot Echoing Equine Disposition Ergo Rider) by SPARKART!, on Flickr.
Some of the connections are tenuous single-stud assemblies, so this isn't really aimed toward playability, but more for giving a sense of scale to a model.
LEGO Bat-pod by SPARKART!, on Flickr.
CHIPS - Central Headquarters Imperial Pursuit Squad by SPARKART!, on Flickr.
LEGO Rey's Speeder on Jakku by SPARKART!, on Flickr.
I hope the assembly instructions are useful and spark some creative applications. Thanks for checking it out.