Found the Galco at a price worth trying and after receiving it, am happy with it. Didn't have any out of battery issues. Just a tad snug but like all leather holsters will adjust over time. For less than $20 figured it was worth it.The Galco speed paddle and mag pouch arrived.
On Amazon it said it fit the MkII. The packaging says Five-seveN USG right on it though.
It fits and holds. Was a little stiff to start and still is, but certainly pulls out of the holster without pulling the holster out of my pants. It doesn't feel quite right, and I have to keep a thumb on the slide for it to not go out of battery when inserting, but perhaps with time it'll break in right. The finish is OK, but doesn't mold in the right spots like it seems intended to (probably looks right on the USG). It will work fine for my limited open-carry use case (national parks in states that don't honor my CCL).
For a long term solution I took everyone's suggestions and also ordered a Tucker Leather Cover Up Plus, as well as mag pouches for the FsN & FNSc
Just spent a week hiking in the mountains with the Five-seveN, alternating between Galco OWB paddle holster (sold as fits-MkII on Amazon but package says for USG) and Tucker's Cover up Plus.
I'm extremely happy with both. I had been leaving the FsN in the Galco to help it mold better (it was too tight to begin with, pushing the slide back out of battery on insert) and it turned out to be a perfect fit.
With both holsters I got to run, climb, drive a truck and ride on horseback with. They both grabbed my Kore gunbelts well and neither ever started to lose the gun. With the belt pretty tight and the Galco at 3*clock it would shift forward to around 2.5* but very comfortable and pretty exciting once I realized it had a perfect grip. So my stance: both spectacular holsters. If I were able to open carry here in my owm state I'd check out the Tucker belt holsters