You sound confident.
Is there a letter from the ATF explicitly stating that the SBA3 and other braces are legal? Right now we have a handful of early braces "approved" by the ATF, and a case where they determined the addition of a brace was illegal. Has the ATF explicitly stated that it was the type of brace, the type of firearm, or the combination of features that influenced their decision?
This whole thing seems pretty grey right now unless you have one of the early model of braces with an approval letter.
Looking at the list of approved devices, it seems like none of them have an adjustable LOP. I wonder if that's one of the sticking points.