That would be abusing the "Caucus" designation. A Caucus is intended to allow likeminded believers to discuss their own beliefs in peace. It's not, however, some magic force field to hide behind, to lob criticisms at another belief. Sola Scriptura is a belief of Protestants.
If you, as a Catholic, wish to criticize it only among Catholics, you'll need to find a different venue to do so. Here, those being criticized are permitted to defend their beliefs.
For instance, there was a thread posted under the "Sola Scriptura Caucus" designation just yesterday, that made mention of Arianism in the posted article itself. Numerous Catholic FReepers bounded hilariously onto the thread immediately to point out that Arianism was a Catholic heresy, and therefore that this was not allowed in a Caucus thread. They were correct.
So, it's not as if there's some widespread problem among Catholics who don't understand how it works. It just appears that protest only arises when the shoe is on the other foot.
Whatever. Then we need a Justification for Tradition thread that is a caucus thread
But what if Catholics wants to comment on P6 aircraft in the context of Yukon relief missions?