It's too late for blossom thinning but the Good Fruit grower recently had an article about a new tool that is being tested for stone fruits (not your apple tree, sorry, but only stone fruits for now). http://www.infaco.fr/en/infaco-products ... roflor.php
Why do I mention this? Because it is my belief that it is only a matter of time before something gets to be implemented for the apple trees.....an engineer with notions of safety and precautions might improvise something like a weed-eater to do the job (with major changes of course, and I don't know what the legal ramifications are).
Again, why mention this? Because it is also my belief that as long as we are putting foot sox on apples, then for those who have pre-established, tall 20 foot trees that they inherited when they bought their houses, then it would be good to find a way to thin out the tops of those trees and only leave the blossoms down where people can reach the apples and take care of them.
This does not answer your question but is only food for thought.....or thought for food, whatever.