[Best way to reinforce PETG for snap on type application]

I have an application where I'm trying to get a PETG object to snap onto rails, I've printed one so far and it just snapped the piece being snapped in. 

 

What do you guys recommend for making something like that stronger? I made it 2MM thicker but I'm thinking it might not be enough. It was with 20% infill and just 2 walls.

[Cura 4.3]

Not sure if I'm beating a dead horse here but does anyone have a way to do a Z axis offset for printing PETG? I'm just getting started and I read you are supposed to offset the Z axis when printing PETG, but I don't see an option for it but just to make sure I asked Ultimaker and they said it did in fact not exist. 

 

I saw some plugins but they were for much older versions of Cura, anyone have one for 4.3?

 

Thank you.

[Z Offset plugin needs testers]

Does this work for the latest version of Cura?