There is no issue building a simple 2 piezo cymbal. Just not a piezo on the bow and another on the edge. There's simply not enough physical isolation assuming you're talking about two bare 27mm piezos. You'd have to put one on the bow and another on the bell. Wire them to a TRS, stick them to the cymbal, make some module parameter edits, and you're done in just a few minutes. From my experience the further towards the apex of the bell you place the bell piezo the better isolation it will have from the bow hits. But it shouldn't be an issue with MegaDrum based on what I've read.
But I don't think that's the functionality CairnsFella is looking for.
It sounds like CairnsFella wants a 3-zone cymbal with 4-triggers.
* Bell
* Bow
* Edge hit
* Choke
This has been discussed in the following threads.
viewtopic.php?f=3&t=174viewtopic.php?f=3&t=286viewtopic.php?f=3&t=293I've yet to see an implemented and successfully tested solution documented here. However, using a modified Hellfire type switch should be usable assuming you can get it to actuate the switch successfully and consistently on edge hits. That's supposedly exactly what this Vdrums user is reporting here:
http://www.vdrums.com/forum/showthread. ... easy+choke Which is effectively a modified Hellfire switch simplified further by using the acoustic cymbal as half of the switch.
I can confirm the Hellfire switch works beautifully as a straight forward choke. I implemented them on my previous DIY build and they work flawlessly. But I've never had a module that can support choke/edge triggering like a Roland or MegaDrum so I've never personally tested one for edge triggering.
Lastly, there's this Vdrum post where someone basically uses a Hellfire type switch on TOP of their cymbal which should guarantee edge triggering since you're hitting the switch directly. And it's not that unsightly even on top of an acoustic cymbal, at least based on the photos. In regards to the Yahama design which uses a bell/edge switch and single bow piezo you could use the Hellfire type switch on the bell as well, though I'd think you'd need 2 smaller circular ones to prevent the curvature of the bell from forcing the switch closed during application on the cymbal surface. But I'm just saying it would theoretically work.