1x10 chainline

Let's call chainrings 'rings', and cassette sprockets 'cogs'. And on my 10-speed cassette, let's call the largest cog '1st', and the smallest cog '10th'.

For Shimano 10-speed cassettes (according to Sheldon):
 - centre-to-centre cog spacing = 3.95mm
 - cog thickness = 1.6mm
 - cog spacer thickness = 2.35mm
 - overall cassette width = 37.2mm

(...not sure about that overall cassette width though - I reckon (3.95 x 9) + 1.6 = 37.15, not that 0.05mm is going to make much difference in practice...)

My frame has a standard (for modern road bikes, but not modern MTBs) OLD of 130mm. And I measure my clearance between the inside surface of the forkend and the outside surface of the 10th cog as (approx.) 3mm.

So I reckon the offset of 10th is 65mm (half OLD) - 3mm (forkend-cassette clearance) - 0.8mm (half cog thickness) = 61.2mm.

In which case the offset for each of my cogs (with proposed gear inches in brackets) is:
 - 1st (33.5) = 25.65mm
 - 2nd (37.7) = 29.6mm
 - 3rd (43.1) = 33.55mm
 - 4th (50.3) = 37.5mm
 - 5th (57.4) = 41.45mm
 - 6th (63.5) = 45.4mm
 - 7th (70.9) = 49.35mm
 - 8th (80.4) = 53.3mm
 - 9th (92.8) = 57.25mm
 - 10th (109.6) = 61.2mm

I'm expecting to spend most of my time in 7th, and that optimum overall chain alignment will be with my single ring lined up midway between 6th and 7th (roughly where the outboard ring would be on a 3x10) - an offset of 47.4mm.

The offset of my single ring is (approx.) 47.5mm (which apparently tallies with preferred Shimano spec.) - alignment is looking good!

So the plan is to start off with no ring spacers, and see if 1st is viable. And if not, move the ring inboard by 1mm or 2mm (45.4mm, directly in line with 6th, is roughly where the outboard ring would be on a 2x10).

NB: the '(approx.)' measurements have been done with a ruler; verniered updates to follow.