Just been up my masts & measured my Main-mast spreader for you. The spreader looks like it’s almost exactly 1.00 metre or +/- 39+1/2” to the edge of the mast. I could’nt get it absolutely exact as I have plastic mouldings on the spreader ends with the shrouds running through them, so can’t see the actual end of the spreader. I think I’ve pretty much got it right though & the shroud would be about 10mm further than that, each side, due to sitting at the end of the plastic moulding.
Mizzen-mast, ditto re’ the plastic mouldings but appears to be 745mm or 29+3/8ths” to the edge of the mast.
I would’nt think it’s absolutely critical, as long as the length is within say, 10-15mm.?
Hope this helps,
Jeff