Is it difficult to remove and reattach the earstems for HJs? My friend has a pair with the ear stems on upside down (how I don't know, neither does he) and I was wondering if that could be fixed easily.

Actually o-matter stems can be turned out easily - but I've allreafy broken one of the small dots on the stems while doing that (on a grapevine). I've not done that with a HJ but with gascans, fives 3.0 and 2.0 - so I think that's no big deal.

I accidently popped one off from a pair of Straight Jackets when I was swapping out lenses. It went back on no problem. I figured it would be pretty easy with the HJs also.

It's a requirement if you plan on swapping the unobtainium, so I imagine they'd design it in a way that wouldn't ruin it if you popped them out. Maybe use a small flat head screwdrivers to pry one of the tabs down.

I accidentally popped off an earstem when I was at HQ trying on a pair and tried to stretch them out a little bit. It popped back in with no problems at all.

Almost all o-matter frames have breakaway temples to my knowledge. Half jackets are the easiest ones to take off and put back on. The easiest way to take it off is to grab it and then twist instead of pulling straight apart. As soon as I get access to a damn camera I can get some pics up to show what I'm talking about.