Updates and thoughts.
I did finally receive the mini water bong with the male water-bong attachment. The male glass adapter slips over the mouthpiece with a little rubber sleeve/gasket covering your ceramic mouthpiece, making it even longer and more prone to falling out of the device with the glass attached. I have to be careful not to turn the device sideways because the slightest wrong bump sends the glass to the floor. I'd definitely try not to use this over a hard concrete surface to avoid dropping the mouthpiece/bong adapter and breaking it.
The mini-bong works well, although it does require two hands to really properly hold everything (or else the mouth piece will be levered sideways out of the device). This makes it a slight pain to use on-demand mode, as you're holding the glass with one hand, pressing it lightly into the legacy pro to ensure the mouthpiece doesn't pop out, and you're trying to simultaneously hold the on-demand button. When I'm using the device native (no water piece), I am always using on-demand mode... but I've found myself favoring session mode with the water piece.
I bought this thing thinking I'd be using the legacy pro through a much larger water piece I already owned using the male bong adapter that comes with the mini-piece, but the mini-piece it came with was small enough and good enough that it gained a permanent spot in my stash box. The convenience of it means I've used it pretty much non-stop since. For a small portable water piece I find it acceptable. It reduces or removes any coughing on higher-temp hits and makes lower-temp draws cool to the extent I don't notice them at all. To be completely frank, the legacy pro puts out cool enough vapor that you don't really NEED a water piece, but using one does noticeably increase comfort/coolness enough that I think it's worthwhile... especially if I'm using wax at the max temp setting. This absolutely reduces the itchy-lung feeling that wax gives me. I still vastly prefer to use this device with flower, though.
As for use... you have to be careful not to overfill the little mini-glass with water. It self-siphons the entire liquid contents right out the bottom of the piece if you over-fill, which surprised me with a lap full of water the first time I did it. Filling it too much or drawing too hard on it also ends up splashing some water up high enough that it'll hit you in the lips, which I'm not a fan of. Once you've dialed in the proper amount to fill (no wet lips, no wet lap) you'll be fine.
I'm still happy with the legacy pro and I no desire to replace it. This thing absolutely gets me everywhere I want to go and I can really dial in the high I want. While it's nice to hit face-melt from time to time (three long draws on-demand at 420F on a fresh bowl is serious business, and doing that a few times in a row will render me non-functional for awhile), it's also nice to be able to get a lighter and more creative/productive high from the same device (I like 340F on-demand, sipping on the device until I reach the right headspace for writing my novels). One loose bowl will get me there, and a re-fill will keep the good times rolling for hours.
Obviously everyone has their own way of using this device, and I'd love to hear what your method is, but here's my own experiments and their results:
420F, ON DEMAND, begin drawing from cold when you push the button, draw deep and slow and steady until the device buzzes (your lungs should hit full right about then), let go of the button, hold a few seconds, exhale. On the second and third hit, wait until the device buzzes before you take your draw. Same deal - long draw, fill lungs, hold a couple seconds, exhale. At this point my bowl is usually looking pretty brown. I might stir and do one more hit, or I might just empty it and go with a fresh bowl because things start getting rough on the lungs after that third hit. I know it's still putting out vapor and I know I could go further, but a fresh bowl is so much more appealing at that point.
Result: Very heavily medicated, comfortable, sedated. Couch-lock is possible, especially if I repeat this with another bowl. I can only do something like this at night, because it's going to put me on my ass. I definitely use the mini water-bong for this, as it keeps each hit more comfortable.
340F, ON DEMAND, begin drawing from cold when you push the button, draw deep and slow and steady until the device buzzes and continue drawing beyond the buzz until your lungs are full. The first hit is pure flavor and light vapor. The next 2-3 hits are smooth and clean with lots of vapor, especially if you take them quickly after the first (before things have had a chance to cool down). The bowl isn't cashed at this point, and can be sipped to keep the feelings going (or you can up the temp and couch-lock yourself). By keeping temps low and being careful not to over-consume I'm able to keep the good times rolling for hours off 1-2 bowls used in this way.
Result: Light head-happy creative high. I feel productive and thoughtful and I'm able to work/write/do things around the house. While I don't usually use during the daylight hours, this does help me punch through the occasional writers block or boring task because it gives me the sensations I'm looking for without the brain-fog. I don't really need the water bong for this. It's usually just me and my legacy pro being used native in front of a keyboard.
YMMV based on individual tolerance, of course, but this is what I've dialed in on as the best methods to get where I want to be.
How are you using the device? Care to share your method and the results?