jCRAN,
your advise is helpfull.
i definitely don't try to invent an Xblade. Just to add a little improvement with no risk. I want to enshure my choices won't lead to dramatic problems.
I will use a VR7 airfoil as main airfoil and a VR8 for the last last section of the tip.
Your advise on 2D calculations sound like an encouragement to go on with that despite of it's unperfection.
Thanks for your help