The 58 is huge though, do you need the extra toe clearance?
No, my toes are luckily not that long.
I calculated that with >620mm of BB to front axle I should be on the save side. Size 56 is actually perfect regarding body position (apart from the seatpost). My next concern is that I would like to fit my full frame bag into the triangle which would need min 45cm of vertical space. Too bad that many frames are having lower top tubes now.
Nice, I tried to get them to do measurements with no luck. Yeah maybe the best option is to go for a nominally smaller tire with the really wide rim 
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They didn't answer your question? I actually asked two different contacts, because the first answer got stuck in my spam folder. The first answer was 60mm in fact. But this sounded a bit unrealistic for a 45mm frame set.
Yes, I think with such a big inner width tires might blow up to the next tire with. The 44mm Tufo could increase it's width by 3mm already. But I would wait until the frame is in your hands to measure the real clearance.
