Congratulations, Geo. I didn't have any problems fitting the Surly centrally on Sugino Cospea crank because the right spacers came with my bike, before they were necessary; they're apparently supplied with OEM Rohloff boxes. Irritatingly, only four were supplied with the Rohloff (I think the actual purpose may be for correct rear brake disc spacing...) but at least they were to hand to measure and order more. I didn't grasp this was a common problem, or I would have mentioned it; I thought it was to do with switching from a single ring, fixed crank system to a compact twin crank and having to adjust to an oddball chain line.
I'm not so sure I'll get the BBB alloy chainring bolts off again because even when using a torque wrench the ali is marginal with that size of torx bit and the bolts were on the verge of stripping. Not that it matters if I have to drill them out, as I wouldn't dream of reusing ali bolts. I bought the ali ones in desperation because they were all I could get in the right length. Very pretty though, in black on the stainless Surly ring. Thanks for the reminder to lay in some stainless chainring bolts when I see them.
I'm exceedingly satisfied with my Surly stainless ring, which in 2600km has shown zero wear (that's getting on for the life of two Nexus ali cranksets with fixed rings already). It is well worth the little extra care required once in its life to fix it properly to the crank.