How do I change default settings for an Autoplace-Control

[Tsevion]

I'm working on some map-gen modding, and I'm using autoplace-controls to add some sliders to the map-gen dialog (as that's the only way I've found to add sliders). But they always default to enabled, and 1,1,1. I want to have them start disabled by default (and be enabled manually or by a mapgen preset I'm adding). I can modify them in presets easily enough, but the default preset can't be edited directly, and I can't find a way to change the default values for an autoplace-control.