Car booster seats with five point harnesses

I've been researching this topic with a parent for a few days, here's where we started:

• Her son needs the support of a five point harness to prevent him from sliding out of the seatbelt in his standard belt-positioning booster with a back.
• Almost all of the harness/belt booster combos on the market today end the weight limit for the harness at 40-50 pounds.  This little guy is already over that.

Guess what, Britax makes 3 harness/belt booster options that accommodate the use of the harness up to 90 pounds!  Hoping by the time he reaches this limit, the need will not be there, if so then investigation into options for larger children will be explored.  Use this link to compare the models:

Britax booster seats to compare

Happy carseat hunting!