I think they're about 40psi; already feel so fun; cant wait to ride! I'v already got 45mm bluemels. I'll get both hangers for now and return the one that doesent work the best; most likely ordering everything from SJS once I call them in the morning to check if they have all of it in stock.
Rear brakes usually tend to be a little longer than front, always had been.
What pressure are they under? the tyres will stretch over time and will be closer to 42mm.
Look like you can easily get away with some massive mudguard too.
Surly will work, my main concern is that it's a little on the long side, hence the other suggestion.