Soft Shackle Eye: How big?

20 Jun 2007
Live in Kent, boat in Canary Islands
Further to my thread about using Selma Fids:

... I have some 16mm Double Braid to Eye Splice. Using the formula, this gives a "fid length" of 16 x 21 = 336mm. The largest Selma fid is 13mm internal diameter (also marked "13") and is 285mm long, which is close to 21 times 13mm (273mm). ...

I'm making eyes in my new 16mm Genoa Sheets in preparation for using a Soft Shackle. I haven't made this yet (I think the core of the Dyneema I'm using is 10mm or 12mm).

How big an eye do I need in the end of the sheets?