I have modified in the past a few Peco N scale code 55
In fact because I found the isolated plastic joiners out of scale I modified them
Today I use exclusively home build Fastrack turnouts in code 55
I simply used the Fastrack method with a jeweller saw to cut slot in the wing rail and in the two frog rail
This end with a isolate frog from the rest of the turnout
To avoid any stress on the turnout when cutting the rails I put the turnouts in a modeler pin vise between two plastic board
If I remember you need to cut of also the Peco wire which are under the frog
On the Fastrack site you can find excellent videos for how to do it
