Just a small idea not sure if they will help very much with shin bang in backseat landings but there are these things called ShinShields here is the website: http://www.shinshields.com/
I've only managed to try them once and they actually made a really big difference, I got sore shins from a backseat landing so I gave them a shot, I was skeptical but they actually made a pretty big difference and reduced the pain quite a lot.
I'm going skiing tonight so I will report back with what I think on my second ski with them.
But really the best way to not get shin bang is with a good boot.
I like to ski with loose underpants or boxers on so my balls can swish around and chill.