ah - next time I'm i the workshop I'll send you my profiles.

basically you need to create a seperate profile for each head. and probably one for dual prints as well - not tried that yet.

I find when you use a specific profile for each head it all works much much better.

It seems weird that the gcode you change is just what head to use or not use, but it definitely effects other stuff as well. Don't know why.
The profile for my Klick-n-print that comes with s3d - drops the build plate abouta mm each layer.
Changed to custom rep dual profile - works perfectly. Yet nothing I changed referenced the layer height or z axis at all.

Also the knp has a weird size build plate that wasn't in the s3d profile. its 234mmx155x150