How much growing room does your ds have before his shoulders reach the top slots of his Radian? (i.e. what is his sitting height bum to shoulder?)
The Maestro does make a nice spare seat. The top slots are about even with the Radian. It only harnesses to 47lbs but it should likely last at least another year to get your son to a good booster age. It makes a decent booster but the headrest does not adjust, so it would be outgrown in booster mode at about the same time as the harness. The only complaint I have seen aabout it that I recall is that the harness straps are spaced quite closely together and some kids complain that the straps dig into their neck. It does not have harness pads to help with this. It is $119.xx at TRU and Walmart, maybe at Zellers.
The Air Protect is the air pillow/cushion technology used in safety 1st seats, with an infant seat, 2 convertibles and a booster using it. I assume you mean the larger convertible seat, the Complete Air? They typically run around $199. They have approx. the same top slots, a 65-lb harness limit and do not turn into a booster.
Another option would be the Evenflo SecureKid 400, also around $199 (TRU shows out of stock and amazon.ca says 2 left in stock). It has the same top slot height if I am not mistaken, and a 65-lb limit. The booster function on this seat does last longer since the headrest adjusts. I guess for me it would be a toss-up between the Maestro followed by a inexpensive booster like a TurboBooster or this seat. The price in the end would be about the same but you either pay now or later. It might influence my choice if I knew the harness rubbing issue does not exist for the SK400, but I haven't heard anything about that.
Also, if he is actually quite short and has a torso of 15" or less, I might consider the Harmony V7 as an option, assuming the install works well; it seems to be hit or miss depending on the vehicle, but I
really like it in my Civic. It is on rollback right now at our Walmart for $79, has top slots approx 16" (~2" lower than the Radian) and a 50-lb harness limit. It also turns into a very short HBB (we are still working out some quirks/questions wrt the highback booster mode) and then what I expect to be a very serviceable backless booster (if the dedicated backless from Harmony is anything to go by).
Hope that helps!
