Combi Shuttle 33 - change in bases?

Problem: the infant carseat we just purchased specifically because it was compatible with my Mustang won't fit with front seat in a usable position!

Background:
We tried the Combi Shuttle 33 in the BRU parking lot months ago to see if it would fit in my 2002 Mustang GT Convertible without rendering the seat in front of it unusable and my husband and I both felt we had a good fit. We weren't ready to buy, as the baby is due in September, but we needed to know that there was a car seat available that would allow me to keep that car and fit all the members of the family in it (DD1 is turning 4 and FF in a marathon).

Recently we purchased the same car seat and an extra base from diapers.com and the seat that arrived is dated 10/09! While it does fit in the car, the front seat can't be used. We're noticing that the car seat is now several inches from the seat back, where before it touched. Does anyone know for sure whether the base has been through any redesign? This one fits fine in DH's 94 Jeep Cherokee, but that doesn't help the Mustang.

We'll be making another trip to BRU to try their test model again and compare bases. Just curious also, would you return the seat based on the date of manufacture? The seat was on special, but was only $30-40 off MSRP.

Thanks in advance, all, for any insights you might have.
Renee

Update:
DH went back to look at the BRU tester and there's no difference. He got a super tight installation that does barely leave enough room for front passenger (though not terribly comfortable, but heck, I'm 38wks pregnant, so what is right now?).

So now my new question; I've made it through the installation instructions twice and can't find anything in there that prohibits touching or bracing against the front seat back. I'm pretty sure there aren't restrictions in the Mustang owner's manual either; we had DD1's Marathon braced in the same position. The front seat will probably be plenty comfortable if we can move it back another notch, so I'm rather interested to hear if anyone knows for sure. I've always heard Britax and Sunshine Kids are the only brands to allow bracing, so I'd like to know if I overlooked something in the manual.