A roll bar in a Boxster is a real uphill battle with the factory top. The problem is (or at least one of them) is that the top bolts to the factory roll bar, the stable engineering bar has brackets to accept the top (which you can se in the photo below). I had a shop make me a roll bar and just didn’t bolt the top back in. Not ideal but the top actually locks in place with the clamshell and front lock. Your top has to be converted to a manual top for this, one bonus is that the top can easily be pulled out entirely for track events. Probably not what you wanted to hear.
