I am intending to replace the metal fitting with the optional soft web strap between the blocks. Rule 18 b. The stainless steel mainsheet eye strap between the two blocks on the boom may be replaced with a soft strap. The maximum width of the soft strap shall be 26mm. The soft strap shall only be fixed to the boom using the holes drilled by the builder as shown in the diagram below. The diagram shows a measurement of 15mm for bottom of strap from boom. This is descibed as 'nominal'. What the *#**$* does this mean? It is not mentioned in the text above, does not say if its a min or max. I presume its a recommended measurement. Any comments. Thanks.