Help with Int/EXT Configuration for Preamps on GSP 1101

[Lost Patrol]

Help! I just purchased a GSP 1101 with Ground Control 2 and have it connected with 4CM to my EVH 5150iii head. I'm able to use MIDI commands to change head channels but am unable to figure out how to change between internal and external preamps on the GSP 1101. I used the config wizard and chose option 7. When I go into global settings the display indicates INT/EXT. When I try to program a patch though, I can't figure out how to select an internal (GSP modeled) pre-amp as opposed to the external 5150. It seems to be stuck on external and all my patches go to external. I have several songs that require VOX / Fender sounds that the 5150iii doesn't deliver well.
The manual does not describe how to switch between internal and external when you are inside a patch and programming the preamp / cab option. Any help will be truly appreciated.

Thanks!!!!!