I've got a Zoom MS-70CDR [multi-effects] pedal, and a few people are saying not to use it via an aux send and return, owing to a comb-filtering issue. Have you noticed this issue with digital pedals on aux returns?
I've always advised my students to set their high-pass filter slope at a steep setting of 48dB per octave to reduce boominess. Is this the best advice to give my students, who are very much at the beginner stage?