Very interesting post Jools. You seem to be saying that although there has been a lot of negativity against EH, there is actually nothing to back it up. There is no evidence at all that EH increases neck loads. There is also no evidence to show that boostering is just as safe as EH. Did I understand that correctly?
That's true. The inverse is also true. There's no evidence to show that EH does NOT increase neck loads. There's no evidence to show that boostering is NOT just as safe as EH. And there are scientifically credible
untested theories on each side.
Since there's not really any comparative evidence either way, all we really know is that
either one, when done properly, is a safe choice. (In fact, my personal, unscientific "gut feeling" is that, for a child who rides properly in either a tethered FF seat or a booster after age 6-7, any safety difference there is is so small as to be pretty much negligible.)
I feel you get to a point where boostering is safe
enough that the convenience and comfort of the child outweighs any safety benefit there
might be. Same as around 4, I'm okay with forward-facing even kids that could easily rear-face 3 more years, because at some point the convenience and social aspects come into play, or I'm ok with a backless booster for a 10 year old even if they are small and would easily still fit a high-back (as long as the fit of the belt is good with one.) The studies we DO have right now show that the
most significant gap in safety in American children riding in cars, more than 1 year olds FF, more than 4 year old 28 lb. children in boosters, is children who are
not in boosters and should be. I'm honestly thrilled to see a 7-10 year old riding properly in
anything, harness, high-back, backless-- because I know they're safer than the majority of children their ages in America.
ETA: and I took so long to write that that I cross-posted. Oops. LOL.