HI I've just got a JMP-1 and I am using the HD500X as a controller for patch switching and that works great.
I've tried the HD into the effects loop of the JMP-1 (Guitar out L&R to Loop return and Loop send to GUitar in on the HD). I get a chorusing occurring, I think its from line level input which I can't get rid of.
I learned that you can go into the JMP-1 - then output into HD guitar in, then HD L&R output to my 9200 power amp. It sounds great but is there any dangers in using it this way (not sure if the tone is a little harsh as it has been using my HD unit and amp sims). Only downside I have is the wah sounds horrific so I'm going back to my cry baby,
ALL THE ABOVE WITH NO AMP SIMS