So the timing window is directly related to the angle of attack, if you shoot an arrow at a much steeper angle you'll have a longer window to trigger it. There's even a feat for doing this (Lob Shot), specifically for shooting over cover. It increases the range increment by one, which seems reasonable for aiming a higher shot (or at least getting a larger timing window). Still doesn't address the issue of what to roll for the timing window.
A better suggestion earlier in this thread was shooting an arrow into the ceiling and triggering the anchor later to drop it on the square underneath it. Still a problem for what skill to use to tell exactly which square is directly above the target (perception?) but the rest should be easier. The AC of a 5x5 square should be 5 (10+(-5)Dex+0size). You'll need to overcome hardness to stick the arrow in. And the final attack would fall under the DC 15 reflex save for half rules because it's not an aimed attack, it's just a dropped object.
As you mentioned earlier - we have timing issues because of HOW a feather token is activated (standard action).
What I'm also trying to get my head around with this odd tactic with an anchor is how you are activating a Wondrous Item when it is not in your possession?
As per d20pfsrd.com:
Wondrous items are usually use-activated or activated by a command word, but details vary from item to item.
Command Word: If the activation is on command or if no activation method is suggested either in the magic item description or by the nature of the item, assume that a command word is needed to activate it. Command word activation means that a character speaks the word and the item activates. No other special knowledge is needed.
(My note: Feather tokens - no activation method suggested, we can reasonably assume a verbal command word activation.)
A command word can be a real word, but when this is the case, the *** holder of the item runs *** the risk of activating the item accidentally by speaking the word in normal conversation. More often, the command word is some nonsensical word, or a word or phrase from an ancient language. Activating a command word magic item is a standard action and does not provoke attacks of opportunity.
(My note: seems like reading the above you should be HOLDING a token in order to activate it - so, once it's stuck in a roof, flying through the air on an arrow, etc - it's no longer in your possession/and you aren't the holder of the item - it becomes, in effect, an unattended object).
So, we have issues of physics, timing and even if possible to activate when the object is not in your possession. Seems like a no-brainer that this tactic isn't going to work.