because I am being a bit thick.
DS is in a forward facing seat but in the next six months or so will be over 16kg and if his growth spurt continues then he will be over the top of the back of his existing seat (Well he is now but not by much)
I did find some handy pictures RE height online but can't find them now.
Also need to see a picture of the best style of Booster... should it ideally have a harness or do I use the car seat-belt?