that is super cool spinsey. I haven't ever seen a slate roof strapped over solid decking like that.
there are a couple variations of French tile I run into that are strapped like than-and then maybe only every other course is nailed--- the rest just hang on lugs.
A few only the bottom and top course are nailed and all the rest are hanging on lugs. ( really speeds up repairs LOL.)
personally--- I haven't been on a lot of slate roofs where the roof was that big----we are mostly residential
for a slate roof--- the Tudor revival style would be the dominate style----and a common feature would be a graduated slate roof.
BIG ,THICK ones at the bottom, and then the courses will bet progressively smallet and thinner up the roof.
Some of the bottom slates will be 1-1/2 inches to 2 inches thick. the biggest slates I encounter are 14x24, 12x24 and 12x22.
we call them barn slates.--- I buy them new, or as salvage--- and then I can cut them down into smaller slates as needed. Many of the Tudor roofs are also random---so the widths will be a mixture of 5,6,8,10's across the roof with a few 12 and 14's thrown in.. Height of the slate is usually 14,16,18 high. It's pretty labor intensive when we are working with widths 5,6,8,10's etc.--- and trying to maintain at least a 3" off set with the courses above and below.
also--- most Of what I buy is Vermont Grey green---- but we use a lot of purple also------------ a lot of the better Tudors will be a mix of green and purple slates, about 60/40--- clear green and clear purple---- occasionally we find some mottled green/purple in the same slates........
I will try to get you some pictures of what we are usually working on.
Stephen