Tan I'm in this situation at the moment. I and E are both in maxiriders in my car but we won't get the two maxiriders plus a meridian for #3 in my car so I'm giving myself all kinds of guilty because I'm "sacrificing" I's safety by putting her into a SnS hi liner with a lap sash. The alternative which I've suggested to R but he just won't go for is that I only ever go out with two children at one time!!

I spoke to Kidsafe over here about what options we have and they confirmed what your links say - they are safer in the adult belt than in an H harness. My I's about your I's weight and height too, so hope that helps.