Should I start booster training?

Do you do booster training? I'm starting to wonder if I should or not. J will be 6 this weekend. He is 48.5 pounds. He has 1/2- 1 inch left in the harness of the GN (as long as he doesn't go voer the crotch buckle first).

He is a bit immature and I'm nervous about him in a booster. I've put him in one for a couple "nearly-emergeny" trips. He didn't do so well. He was in 2nd row, and A was in 3rd row. He kept turning around, and out of the HBB to see and talk to her In my van they are both in the 3rd row, so this may not be much of an issue. However, in Mom's van, J is 2nd row, A is 3rd row. With the setup in their van, I doubt Mom would be putting J in the 3rd row. Mom and Dad asked about putting him in a booster a couple months ago, and I asked them to wait until spring (thinking less winter driving and he'd be 6). I think their booster desire will go away once we don't have to deal with coats.

So, should I start booster training him in my van, to know he'll do well in Mom's van if he is switched to booster? Should we try it out in my van so I'll know he'll do well when he outgrows the harness? Should I ignore it and pray he makes it another year in the harness? I can't afford another seat for him on my own, and his parents won't buy another seat either.

I started helping kiddo get used to sitting still in the booster indoors for progressively longer times before her 4th birthday. Although she was still RF in my car, she had to stay with my parents during college exams & they have severe arthritis + nerve damage. They can control the wheel, but could not buckle/tighten harnesses, so she had to use a booster: the rule was simply that they lock the shoulder belt & 1 adult focused on kiddo while the other focused on driving. She just turned 7 & I finally feel confident saying she is now capable of sitting correctly the whole time, even with other kids in the car (unless they're really invading her personal space & then she becomes an overemotional wreck, forgetting correct positioning). So, over 3 years worth of booster training, which included her sitting in on some relevant seminars/workshops She was capable of teaching correct booster use to her PreK classmates, but it took another 2 years for her to really practice what she preached

I can't even get my tweens to sit still in their boosters if they are in the car together and not right next to each other I think there's hope for even your wiggly guy if you remove the temptation of someone behind him or if they are both outboard (mine are always trying to look at the same toys in the empty seat between them...reaching out sideways and leaning to look, kwim?). I have to put them right next to each other, then they sit reasonably still. When only one's in the car? They are angels

I would. With Michael in a booster, I am always having to remind him not to slouch and to sit right. He would still be harnessed if it wasn't for his car sickness.
Logan has been in a booster 2 times in a dire emergency and he sat perfectly still(I knew he would be like this-no suprise, but still way too small or young to be in a booster). I will probally booster train him when he hits 40 pounds, but still be in a harness 99% of the time.

I say start training him if he is that close to outgrowing his seat.