I'm a pretty handy home mechanic and have never had tire mounting problems until now.
I've had fine luck with Bontrager, Reynolds, DT 411, DT Spline, WTB, Pacenti, HED, etc.
This DT 1.1 rim seems to have almost no center channel it's pretty much straight across. I've never seen anything like it. General internet chatter seems to mention the difficulty of mounting tires on these 1.1 rims. The Open Pro is difficult, but doable. The DT seems to have problems with any tires that are made to tubeless compatible specs.
My main concern is just being stranded. When I got the bike it took two tire levers and a screwdriver to remove the Schwalbe tires that came on it. I know that was bad form, but I had no other options at the moment. If I got a front flat even with the tires I have on the rims now, I still don't think I'd be able to fix it on the road. To further the story, I then put those Schwalbe tires right on my Pacenti Forza rims by hand and with zero problems.
My only other thought is to check overall tension of the wheel. I've radially trued many wheels. Maybe it just needs to be pulled in all around... which also seems like a bad idea.
Anyway, that's my story.
Thanks everyone.
Ben