In my custom vehicle I am creating I want to change the character position from a seated (the default) position to one where he is lying down on his stomach, like in a hang glider. 

 

My first thought is that this would involved extending RenderPlayer and setting up some custom code in there, perhaps modifying parts of sleeping and rotateplayer.  Is this the best way to go?  If so, what do I need to register so the player gets my new renderer instead of the default one?

Also, along similar lines.

 

I want my player to always face forward in the vehicle.

 

I thought something like:

this.riddenByEntity.rotationYaw = this.rotationYaw;

in the onUpdate() method of the vehicle would do the trick, however it appears to make no difference at all.

Probably need to override

Entity#shouldRiderSit()

and

Entity#updateRiderPosition()