Tips or tricks needed to delete double faces

skydoll

So i have been working on this old max scene, where they still had to use double sided faces to show both sides of a object.
To improve the scene's performance i would like to delete one side of those double sided poly's

I have read quite some thread's on numerous sites.
But i couldn't find a good solution.

I did try the following scripts, DDF ( delete double faces)and find co-instance. they worked fine on simple scene's. Like self made double sided boxes, but not on more complicated scene's like buildings.

So i was hoping there was someone with a trip or tricks up there sleeve.
To help me out

Thanks, Ciao