Hi all! is there a setting in the aircraft cfg that can be altered to increase the reverse thrust?

That will be in the .air file.  Search the library for "AirEd152".  It's the freeware program for editing these files.

It's table 313 in the airfile and the negative value is throttle percent.

You will also need to check the engine limitations schedule of your a/c so that your engines do not exceed the set thrust value for full reverse.