Mature apple tree pruning

[Hank]

Hi guys, hope everyone is doing well. I looked at a few pruning topics but couldn't find anything that really answered my questions (although I did pick up a ton of good info).

 

Some friends of mine have this mature apple tree in their garden which they love, it provides them with a good crop of cooking apples every year and is a feature of their garden. They want to prune it which I said I was happy to do but I just want to get the balance right.

 

My plan so far is to open up the middle a bit, remove dead and crossing/inward/vertical branches. Is there anything else I should be looking at? Some of the shoots are fairly chunky now, should I be reducing their number or focusing more on smaller branches/shoots? I'm looking at removing about 20% of the canopy overall.

 

Thank you!