First, I'm not sure JHV3 is still taking new work. I seem to remember getting an email about it a year or two back.
I had JHV3 mod my Line6 FM-4, not the same but perhaps similar. He was a real pleasure to deal with via email, had a reasonably quick turn around (I had another analog pedal recalibrated at the same time), and inside his work looks top notch. Absolutely recommended. The Line6 models didn't drastically change (not the purpose of the mod), but the tracking on the synths improved a bit, volume drop was fixed, and seems to be just a hair "better" sounding. I would posit the same results apply to the M9 mods, as a lot of the same things are addressed.
First the switches stopped working occasionally so I replaced them all with proper mechanical switches. Later the tap tempo function disappeared, even though the tap switch still works for entering the looper or changing scenes. Now it started to forget the values of presets with enabled expression pedals. It really makes me angry that I will need to buy another one of these even though I already know it will not be relieable after a relative short amount of time. Still it is one of my most used pieces of gear and I need it for almost every track with my band so there is no other way. Why does this thing have to be so good and so bad at the same time?