FSX, PMDG 737-800, PM CDU - Configuration

Ok, so i am starting to lose it here. I have read thread after thread about the various 737's in FSX and which files to use etc.

I am using the PMDG 737-700 in FSX without a panel. I have the 737800PMDG text file for the CDU and mostly it works fine, but no matter what i do the aircraft is always too heavy and struggles to get off the ground. Plus all my V speeds in the GC just seem to be plain wrong. It doesn't seem to matter even when i have the center of gravity figure correct in the CDU.

Help???????????

Please, someone that has built a working 737 cockpit and use the PMDG flight model with PM, let me know exactly which files you use, plus your payload settings as well.

Thanks.

Regards
Ben