Freya the new Infa Comfi Caprice convertible boosters have shoulder markers of 520mm, the Varios are 470mm. If you could afford it they may be an option. Do you know their seated height? You know torso, bum to shoulders I think the SnS Maxi Rider Easy Adjusts are quite generous too, but they cost an arm and I leg I think, Infas are more reasonably priced. Sorry for my extreme mush brain today too but don't they need to be in a booster until 7 now, or did I dream that? I know they need to be harnessed until 4 and thought booster until 7, or maybe that is what the next change will be. I'll have a check.