I just did a quick fit-up to check, thread-wise they screw in fine so there's no issues there. (Pics below) I used the original boss plates that were left on the frame as a spacer, although I have ordered up a curvedshifter bosses plate to just do a double check as it was only £1.

I'm actually a bit worried now if I've cocked-up and have the wrong shifter levers!