To make the Perdix as liberal as the Geo, you would have to set it to something like GF95/95. Some might say GF45/95, but for non-deco dives, it's really the GF Hi that matters so 45 vs 95 for the GF Lo doesn't really matter.
I have dived the Shearwater (Petrel) + Atom (basically, same as Geo - i.e. using DSAT algorithm) comb a number of times.
The system I arrived at for myself to use is that I will stay down for as long as the Atom NDL allows me. That could easily put the Perdix/Petrel into deco. Especially with the default Medium Conservatism setting. Then I will do my ascent, doing any stops that the Petrel/Perdix calls for, including a 3 - 5 minute stop between 15 and 20 feet. Normally, the result of this approach is that, at most, the Petrel/Perdix calls for a stop at 20' that is no longer than what I would do as a safety stop anyway. But, if it's 6 minutes instead of 5 or whatever, it's no big deal - and it eliminates any guessing.
This results in what I think is a very safe dive with maximum bottom time. And I know that, by not exceeding the NDL on the Atom, I CAN always go straight to the surface, if I need to. And I can also get back on the boat and say truthfully that I did not exceed the NDL of my Atom. Some boats do not want people going into deco, so having my Atom show that I did not go into deco may or may not turn out to be important.