HBB weight limit v height

[PinkyCheesy]

DS (10 1/2) uses Maxi Cosi Rodi, which says its for up to 150cm / 36kg.
I don't want to stop using it as DS finds it comfy, often sleeps in it, and it protected him hugely when we had a car accident last year.

But he is now 35kg and only 139cm. Does the weight really make a difference if he stays in the seat to 145cm (which is the European height regulation)? Obviously I don't want him to be at any risk. Can't ask anyone in RL as all my idiot friends' kids have been sitting only on booster seats since age 7 (don't get me started on this!)

Thanks in advance

Mine 2 dd aged 6 and 10 will be sitting on theirs until cm as that is the height adult seat belts are designed for uk law is 135 but in Germany and Ireland it is 150cm. In Germany it is 150 or 18year which ever is soonest. As they don't seam to have any different seat in Germany I conclude that its ok to go over the weight.
I want mine to sit in theirs as we do some really long journey when sometimes they fall asleep