I've been looking at the script analysis of the Bedford Hours in Michelle Brown and Patricia Lovett's "The Historical Source Book for Scribes"
I was avoiding it, coz I felt it was cheating, but I've had 'feelings' about the diamonds, and there is also the spacing issue, so I looked.

First - the diamonds.
They are not built up diamonds in this script after all! At the original size of this picture in the book, the diamonds measure 3 mm x 3mm (and the verticals are slightly offline to the centre of the diamond, as Drogin mentions).

*groan*
I realize that I've gotten a bit ahead of myself - I haven't done the formal script analysis yet - but I wanted to do some basic pen stroke practice appropriate to the Bedford Hours as practical work while I did the mostly paper work of the analysis, and I've found myself dragged into this confusion.
I should have done script analysis, and measured the diamonds vs p.w. first, instead of just looking at their particularly pointy ends and thinking 'oh, they must be built up, so I'm going to practise built up diamonds".
Don't I feel silly.
But once you've made a mistake, you don't tend to do it again (you hope). And now I've had practise with built up diamonds, for when I do use them.

On the verticals : the image very handily has vertical lines drawn through the verticals of most of the letters. And they are all 5.5 to 7 mm apart. I think this is a reasonable case for saying that all the verticals are evenly spaced - allowing for enlarged error because of the enlargement from the original, and also human error by the scribe. There is variation when letters are ligatured, of course.
Well - no kidding! 1 p.w. It says that in all the books. So in this case, inter letting spacing should be 3 mm = p.w. Plus, to have the lines going through the centre of each vertical line - that's another 1.5 mm (half p.w.) multiplied by 2 (right hand and left hand edge of each vertical respectively) = 3 mm, to give a total between the verticals of 6 mm. (where I measured 5.5 to 7 mm)

I have been getting myself a bit confused. There is the same space between the verticals but I've talked about the same space being between the *diamonds*. This is true for m, n, u and i, because they have diamonds above their verticals. So it's effectively the same space as between their verticals for these letters.
Won't work for the rest of the alphabet tho.

I've really got myself in knots because I was looking at the Gods of Snow quote, and noticed a fundamental problem with my script - that I was varying from the pen width for my inter-letter spacing to make the script more legible to my eye.

I have been practising looking at the space between each diamond as i draw/write it with my m,n,u,i.s, I'll have to swop over to verticals, so the practise is useful/relevant for when I hit the rest of the alphabet.

I know, I know, I know - that both inter-letter (ie counter space) and intra-letter spacing is 1 p.w. I just seem to have picked up a bad habit somewhere. I can understand why - making it more readable. It just isn't correct. And I've practised so much - it's kind of ingrained now. *sigh*
I'm very glad that I have finally picked up the problem from looking at historical examples.

I am getting a bit tired of being stuck on this issue. It's so simple!
I will work it out.
I definitely think too much.

Did I mention that anyone reading this might end up confused, coz I was?
Behold!