How to square handwriting variation?

[oshfdk]

I know this is a frequent issue that transliterators come across and it is also an issue for any sort of solution to the script itself. These three EVA-sh ligatures (see below) on f4r are all in a row but all have a different form and shape. How can one square these differences? This page was written by scribe 1 which tends to have the best handwritting out of the scribes as well which makes it even more confusing. 

If you consider the size of the text, the variations are not that big. When I try writing really small letters, even with a good writing tool, the shapes vary a lot, because there is a limit to how precise you can be with the direction and the position. I can keep it neat for a few words, but I certainly won't be able to keep precise shapes for pages, and the moment you relax your control it gets comparable to the Voynich MS variation for me. 

Here's a Voynich MS page with a standard USB plug roughly to scale, from the known dimensions of the MS itself.