Answering my own question above, contacted JDS Labs and they replied in like 100 milliseconds with the info, amazing. For those interested adding an ODAC board should be a fairly simple affair, soldering required.
EDIT: not necessarily true, MD's O2 is not from JDS, see my later message https://www.massdrop.com/buy/massdrop-o2-amplifier/talk/518058
573V0Yes it fits. You need to buy a new rear panel with the hole for the USB, and some nylon mounting screws from JDS, $10 and change. I guess you can drill the hole out too, won't turn out as clean but being on the back not that big of a deal if you ask me.
EDIT: while true for JDS products this doesn't apply here as MD's O2 is not from JDS, see my later message https://www.massdrop.com/buy/massdrop-o2-amplifier/talk/518058.
573V0Ugh, O2 is open design and I've just realized that I assumed this was a JDS Labs version, but chances are it is not. I came across some info previous drops were from Mayflower or some other overseas company. So now I'm now less sure about the ODAC mod. If the amp board is the same then sure, but if not there can be issues. JDS Labs rear panel is almost guaranteed will not work with this enclosure, so drilling out is the only option. Also there was speculation that the O2 offered by MD used inferior components, not sure if that is true. Can anyone confirm the manufacturer of this O2?
g_v_lIf it is from mayflower, they aren't an over seas company and they actually have an o2 to o2/odac conversion video guide on youtube. (not sure whos making this drop though)
EDIT: not necessarily true, MD's O2 is not from JDS, see my later message https://www.massdrop.com/buy/massdrop-o2-amplifier/talk/518058