Battening for slates, not matching ridge

Hi. I am felt and battening roof at the moment. It goes from meeting the old roof, to going round 2 hips and ending in a grp valley. I only have a few pictures at the moment but will get more on the weekend as now covered up.
I have Layed first batten in line with the old one at the bottom. Then found the distance from edge of new roof to top of the new batten and followed thy round the roof. From there, used a gauge to keep going round. This works well and puts all new battens in line with old. However, all measurement match up the whole way round but battens don’t match up on the second hip and Am unsure why. Additional to this, measurements are right from roof edge but am about 30mm out from ridge meaning that the battens are going to be well out either side. I may put extra battens in if needed but am worried nothings going to match up. Really don’t want to rip it all off and start again as not sure what could be done differently. Hoping any discrepancies can be hidden in the valley and hips but not sure how to tackle the ridge tile. Any thoughts? Hope my explanation is kinda okay!!?

If you are using slate the gauge is set.
It's a small rafter length and once the hips bedded on it will make little difference and it may not even display.
It needs a batten running each side alongside the hip rafter to give you better fixing options .

Just a follow up. Finished the battening yesterday. Battens by the top are about 15mm difference which is good. problem was the wall, our new wall bows in slightly and as we measured from end of fascias, the battens on that side are slightly ****ed. So I have got more exposed slates at the top on one side but that’s okay, I can just have what will look like a slanted ridge on that side.

someones going to have fun

Plenty of cutting!

fixing the cuts

Is that a harness?

Tied to a batten?