I've finished building up the frame and hope to bring it out on it's first ride this weekend when things dry out a bit. There's two things that I wish I had known before ordering this frame.
1) the frame requires a crank with a 55mm chainline and is not advertised as such. This would be fine if I was purchasing a new crankset. Since I was using an existing SRAM X0 GXP crank, I had to get a new chainring with a 0mm offset to get the required chainline. Even with the 0mm offset ring, the clearance is tight with a 32t ring. More on that in item 2. For my daughters frame, I was planning on using an existing 3x SRAM Stylo GXP crank. It's a 1x drivetrain so I was able to put the ring in the large ring position which is roughly a 56mm or 57mm chainline. This set up has plenty of chain ring to frame clearance with a 32t ring. There was no chain jumping while back-pedaling in the large cog so all appears to be good.
2) a 32 tooth ring is probably the max that will fit comfortably. If you don't plan on going bigger than a 32t ring, or a 30t oval ring, you should be fine. I don't have an oval 30t to test fit so I can't say if that would fit or not. This is more of an issue for me as I'm trying to run the Philcentric EBB. A 0mm offset 32t ring still will not work when the EBB is in the aft most position. This will limit the amount of adjustment I have when getting the chain tension correct. Everything went together fine with the 32t / 18t gearing and the EBB has the spindle in the lower forward position. I could not get the 32t / 20t combo to fit but that is partially due to the limited adjustability of the Philcentric. This combo could work with a half link but then finding a 0mm offset ring that doesn't have a narrow wide tooth profile would be difficult.
I will say that while I was trying to work all of this out, the folks at SP-Cycle have been very responsive to my concerns on the AliExpress chat. I always expect the worst when dealing with some of these direct vendors so any type of help is appreciated. This frame definitely isn't for everyone as it does have some concerns, but those concerns will not apply to everyone. If the ride is as expected, I'll probably be ordering another one to build up for my brother. That will have gears and a new drivetrain so we purchase the correct parts in the beginning to save some hassles.
My other option would be a chain tensioner where a rear derailleur might go.
I think that would be a safer option with this frame as a single speed.