Prusaslicer is using the designated support material to build the draft shield  

Prusaslicer is using the designated support material to build the draft shield

I'm currently printing a 3-material object, while also tinkering with the model in Prusaslicer.
I'm printing in PETG, with PLA supports. In the slicer, I can see the draft shield has interleaved layers of PETG and PLA.
Is there a way to tell the slicer to only use a certain material for the draft shield? To tell it to NOT use a certain extruder for the draft shield?

I'm concerned that the draft shield will fail, mid-print, and spaghetti all over the objects it's supposed to be protecting. (Enclosure parts, so in the future I won't have to deal with draft shields, as it so happens.)

In MY case, my support material is cheaper than the base material, and it's the poor adherence that I'm relying upon, that is also the source of my concern. However, if I WAS using soluble filament, $80/kg soluble filament, I certainly wouldn't want it wasted on the skirt then either. Not even just a line here or there.