I've tried the affix, turbo booster (regular, not the safe surround- that's next), Monterey, and parkway SG. So far the affix is the best fit, but nothing like the nautilus. We have to replace that due to an accident, and it just seems silly to buy a new nautilus to use it as a booster. The children in question are nearly 7.5. What else should I look at? The issue is the way the belt fits in the guide and retracts, and ease of buckling.