Minecraft Version: 1.12.2
Forge Version: 2709
Mod Version: 0.7.2-234

This is some general feedback on the new armor mixed in with some minor issues:

• [General] Some features seem to eat through air really fast, it feels like you need about two full stacks of volume upgrades per piece to use the armor for more than a few minutes. (I was rushing through features though, maybe I just overtaxed it.) - Needs more testing on my end. 😄
• If the armor runs out of air it keeps looping some sort of "clicking" sound in rapid succession. - It does the same when you turn it off via the U-Screen.
• [Bug? FPS] Stepping on a charge pad with dispenser and 10 speed upgrades dropped my FPS to 1. removing speed upgrades gave successively better results, at down to 7 or 6 it became bearable. - Note: I also had the chestplate charging other items. Charging loop? Bad interaction?¹
• [Boots] The flight mechanics are just AWESOME!! Zooming about my world has never been that much fun.
• If you press the flight hotkey while holding space (and flying) the boots turn off but you keep zooming about in flight mode. You have to turn the boots back on to stop. (They do keep using air.) Is this intentional? I slammed head first into my refinery and got an exiting new death message. 😆
• On a related note: Is there a way to unbind keys in the armor config screen? ESC just closes.
• I have 10 bars of air pressure in my helmet, but I can't siphon off a little of that to breathe underwater? Really? 😛

Overall: This is gonna be fun! Some interesting mechanics, not just bigger protection numbers. - I'd love a toggleable night vision but I can't really think of a way to thematically mesh that with air pressure.

¹I used a creative pressure source at 20 bar + 1 adv tube + charging station.

@desht 1st point - I know this may be an old-hat solution, but what about an RF Compressor upgrade that could resupply the air? Similar to how babbles and other tools that require energy can be charged on the go via capacitors (https://ftb.gamepedia.com/Resonant_Flux_Capacitor) or something similar. I understand if you don't want to go this route, though.

Another option - what about the currently existing Air Canisters? You could make it so shift right-clicking one will make it share its air to anything that needs charging. Possibly we could also combine them into medium, large, huge etc air tanks? Somewhat similar to Volume Upgrades.

That's basically what the chestplate plus Charging Upgrade does now. The chestplate already has a large volume compared to the other pieces (28000 vs 12000) and can take an arbitrary number of volume upgrades, so can store and supply a huge quantity of air.

Thanks for the feedback, it's always welcome! To address your points:

• Air usage is something that's definitely open to review. None of this has really been tested in a proper survival playthrough yet, so adjustments are totally on the cards. Having said that, my aim is to have the armor (relatively) cheap & easy to make, and therefore have the challenge be to keep it pressurized. Which means lots of volume upgrades earlier on (especially in the chestplate, with charging upgrades), and the Aerial Interface later on. And a good pressurization infrastructure at all times.
• I've not encountered the sound glitching when air runs out, but it could be due to one piece running out, getting a little air from the chestplate, starting to re-initialize, and then running out of air again perhaps? Can you describe the events that lead to that in more detail so I can try to reproduce it?
• Yeah, I'd noticed FPS issues with the charge pad too, although not quite that severe. I will take a look into it, though. The charging station code may need a little reworking to handle high numbers of speed upgrade more smoothly.
• Glad you like the flight mechanics :) I'm fairly pleased with how that turned out.
• I'll take a look into that (turning boots off while holding space). Probably an easy enough fix.
• Unbinding keys: I wanted to do that, but it turned out to be harder than I hoped. ESC gets caught and closes the GUI well before that screen sees it, unfortunately. The solution is a fairly significant rewrite of the whole GUI, or maybe just having shift-right-click unbind the keys. And of course the keys can be unbound in the normal Minecraft config screen.
• Yeah... that had occurred to me, but that's something the Aerial Interface does already, and I didn't really want to step on its toes too much. But it does make very good sense. I dunno, maybe some kind of more limited air supply from the helmet?

Think I've addressed all the issues you raised other than the looping sound problem, which I haven't been able to reproduce. There will be a new 0.7.3 release with all these fixes in the next couple of days.

That was fast. I haven't even built up all the infrastructure to get the full armor in my survival game yet.

I better get on with it 😁.

Go for it :) I'll be interested to see how the air usage balance works out for you...

Note that 0.7.3 is uploaded now (awaiting approval). Going to leave this open for now since it's a useful place to continue discussion of the new armor.