Trouble is, back to the no-regulation thingie. I don't think that the newest Boulevard (where the wings are essentially flush with the side of the seat) is any safer in a side impact than the, say, True Fit, with its nice deep shell.
Now..my Wizard...that had some SIP going on!
it doesn't take wings to make SIP. a deep shell can be considered SIP as well, as long as it contains the head in a side impact. the como doesn't have wings, but it has a shell at least as deep as the TF's, and it is marketed as SIP.
sure, there's lack of regulation, and carseat mfrs can market anything as SIP if they want... that doesn't mean that a seat marketed with SIP
won't perform better than another. and personally, if reputable carseat mfrs who do their own R&D and have decades of experience in designing seats for airplanes and race cars (like britax and recaro, respectively) market their seats as SIP, i believe it far more than other companies who make similar claims.
i think a lot has to do with logically looking at the seat and reasoning that it can contain a head in a side impact (as you did with the TF). those videos of EU boosters in side impact tests are pretty convincing, and the ones that did the best job looked like they would just from looking at them standing still.
there's also lack of regulation concerning RF tethering, but there's a camp of CPS-aware folks that believe in it and will use
only seats that are capable of that... it's fine to have a personal preference based on logic and instinct but lacking in publicly available data or regulation. do i *know* my DDs are safer in a side impact than if they were in radian 65's? no, i don't. but i have a personal belief and when we are faced with infinite choices but limited data, we have to rely on a personal belief to guide our decisions.