Hey Jane, thanks for that
I think you might be right, on days that i saw that he could handle a bit more A time, it appeared that his night times were better. also, i don't know if it makes sense but also when i put him to sleep at 2 hours after a very calm 2 hour A he actually started sleeping less. wakes up after 1:30-1:40 but it never seemed like he woke tired. So intuitively to me that says - his brain can probably manage a bit more.
I'll give it a go - start with 2:05 - 2:15, depending on him.
Thanks.