Haven´t tried, but in the pb forum Psychophanta wrote that you can handle a sprite in a 3D world like a 3D object.
Why you doesn´t try that with collisions?
If it doesn´t work you can post your code in the pb forum and maybe anybody helps you.
Thats how a forum work.
And just 2cents from me....why you switch between engine/languages every few weeks?
Stand by one and work hard with it and you should found a solution for near every problem.