Just got my Allen Edmon shoe trees in for my fifth street boots. The size guide indicates that a 9D calls for a medium shoe tree. I'm telling you though, it was not easy getting them in. And even when I did there is some space between the shoe tree tip and the tip of the shoe. Is this to be expected?
I am TTS 9.5D, but I do wear 5 lasted AE shoes in 9D.
For calf I mostly use split-toe trees from Alden or BB - large.
For shell I mostly use full-toe trees from AE or JAB - medium.
Doing the above, in my experience, avoids the problem you are experiencing; the medium AE trees in full-toe have much more girth than medium (or large) split-toe trees (whether Alden or BB), and the split-toes should go to the end of the shoe (they do in all of mine). The extra girth of the full toe, IMO, is nice for shell as it better "fills up" - i.e., slightly stretches - the shoe allowing for the smoothing out of rolls. And a full toe tree in large - for my shoe size - would be overall too big.