Advice needed

[Numplumb]

Hi everyone I'm looking for advice regarding the rear wishbone brackets for the MX5 build.
The book shows a measurement of 220mm from the build table to the centre of the top suspension bracket NTS alterations doesn't show a measurement is there a set distance between the upper and lower wishbone if so what.
Also the MX5 build shows a measurement of 90mm to the centre of upper wishbone bracket if I move my diff back by 20mm and make this measurement 70mm does anyone see a problem with this, I mocked up the suspension and it clears everything at full travel so I can't see a problem, the reason why I would like to do this is because my chassis has the upper damper brackets fully welded as per the book and I don't want to cut them out and move them forward by 20mm as the NTS say if I can help it.
Regards Mick.