Here's a pick of what has to be cut away in an IV3 12 for the thumb screws. This is the thinner of the two STL that printbus linked to.

IMG_20160303_075338965.jpg

260C and a 1.02 multiplier gave much better results with the PETG. Still not perfect but much better. I still get a bunch of loose strings in the nut capture area of the thumb screws though. Would a cooling shroud help PETG like it helps PLA?