That was indeed the thread that got me started on this ABCbut when I tried to find it again I failed - I always have a problem with search engines. But, thanks, I'll make a note of it. Elsewhere I found another guide - and I've mislaid that address, contained the name "walshaw", I've got it here somewhere.

As for the E/ or E/2, if I undersood it rightly either is acceptable. Mind you, that's a big "if".