Set the wrong paper and hope, also never admit to it, since the reason it doesn't is that it damages the roller and will eventually cause the printer to jam lots. It also tends to damage the output. It's pretty OK here and there, but if you do it lots it will absolutely cause problems.
Looks like I solved my own problem. It seems that the printer does not allow duplexing on thick card stock, only regular card stock. is there a workaround for this or do I need to just set the wrong type of paper for it to work?
I have a phaser 7500 that used to print duplex but doesn't now after a new computer/driver install. Driver is global driver V4 PS.
I am able to choose to print on both sides int he printer options or natively in the program I am trying to print from. All looks good but it still prints on 2 sheets.