Thank you for for reply Andy, much appreciated! I have used your Physics Helper in 5 apps/games, and I really enjoy using it.
I will try out the old Physics Helper and target WP8 when i get a dev environment up and running. From what I understand the MS App Hub supports multiple XAP's for one game - so one game can target both wp7 and wp8. See here:
My game is Portal Ball:
From feedback on mail, and reviews (bad ones), I get the impression that WP8 phones (Lumnia 920, HTC 8x, Samsung Ative) often have trouble. A friend of mine have tested on a Lumnia 920 without problems, so it is a bit inconsistent.
It would be great if you can test it on your wp8 :)
Some notes on the implementation:
* Didn't get BitmapCache to work, so had to drop that.
* If i use EnableRedrawRegions the ball flickers and all kinematics (elevators etc) flickers. If I add BitmapCache the flicker stops, but everything gets sluggish. Strange!
* The game performs good on my WP7 (Samsung Omnia 7) - a few levels are a bit slow.
* I am working on a new Portal Ball game now that have upward scrolling (using camera) - and here I have to use BitmapCache on most of my elements to make it run smoothly (use the same UserControls as Portal Ball).
Thanks for all help.