I wondered whether anyone could give me some advice0. My son is autistic/ possible genetic disorder too awaiting testing, he will be three this month. Anyway at the moment my son is in a three point harness car seat, however is getting too big for this now. I am very anxious about putting him in a booster as he can already take his arms out of the one he is in now. I wondered if there were any specialist car seats or straps out there to make him more safe. ta x