My wife bought some sleeves that go around the belt from Autozone or Oreilly’s Auto parts. It takes the sharp edge away and distributes the load over a larger area. Might be worth a try.
I have run enough calls where someone was ejected and ended up under a tire or under the vehicle to make me a believer that my odds are better inside.
I have also seen a “large” woman with a large ring of keys buried inside the adipose tissue of her leg after she rattled around inside of what would otherwise have been a fairly minor wreck.
Even wearing a Tee shirt isn't possible for me anymore {for over 20 years now} because of the closeness to my neck. The distraction the shoulder strap triggers in me is a far, far, greater risk to myself and others safety than me not wearing a seatbelt. If moved about three inches down I could handle it. I could cut the shoulder belt portion off I suppose {as I did on a van I once owned} but that makes it useless to others who can use it. I better stop here or this will become a rant against the unending onslaught of Nanny State Laws. LOL.