i don't have to ask snowolf.
riding with a backpack throws you off. period.
riding with a backpack at the resort, unless you are filming and carrying DSLR camera equipment - is stupid and will slow down your progression.
i have fallen into treewells and volcanic vents. i have fallen in upside-down. i have lost friends to tree impacts.
what you need is solid skills. if you want to survive a treewell get good at manipulating your binding straps. be able to reach them while upside down. wear a helmet to prevent being knocked unconscious, sure - but wearing an avalung in a treewell is just going to give you another 15 minutes in a situation where noone is probably looking for you anyway.
avalungs were designed to give you time to breath in an avalanche burial - dense, compacted snow and (hopefully) an active rescue. treewells are different. the snow is not dense and your friends are either right there (watched you go in or noticed you missing on that run) and are digging you out or noone watched you go in and its up to you to get out or we'll see ya in the spring.
i get the feeling i'm not going to be able to convince you i'm right here - and you're free to do whatever you want, but you'd be better off with a lifealert bracelet or a 2way radio in a treewell situation...