I always wear a collared shirt when flying so that I can raise the collar and protect my neck from the strap edges.
I use a cable tie to keep the two straps together on the bar but the assembly can still slide along the bar. I have to remember to center it before laying the straps off to the side when getting in.
I've had thoughts of some sort of retention mechanism to keep the straps centered but it's a low priority item.
Flying RV-8 N880BC
2021 Dues - happily paid.