It would be beyond my level of comfort, too.
There are times when I willfully defy the manuals, but those are when the other option is worse. I have our young friend sit in an incognito in our front seat. The booster says never to place in front of an airbag. The child lawfully does not need a booster. She also routinely rides in the front seat of her mother's vehicle. ( she is only in the front when we have no space in the back.) The way I figure, she has to be safer in the incognito than not. The belt fits her better and she sits a touch higher up.
I'm also wondering what his ff seat was. IMO, he was awful tiny to sit ff, and some convertibles, like the cosco ones, have height minimums....