I have just been on the Essex car safety website and seen that they recommend a high back booster (rather than just a basic booster seat, for up to 11 years). I have therefore dusted off my old Maxi Cosi Rodi for my son (7). However, I need to sit him in the back seats (seats 6 and 7 in the the 7 seater PIcasso). The way the straps work it just does not sit properly over the Rodi and if he leans forward they do not retract (so not very safe). Does anyone have a 7 seat Picasso and a high back booster that work together in the rearest two seats? Any replies gratefully received!