I have a Larue 9" that I'd like to pair with a quality upper. John doesn't sell Larue so he can't tell me if his Ultramatch upper will work with the Larue handguard. The concern is the Larue anti-rotation collar that intertaces with the upper. I know on the first VLTOR MUR this was a no-go (now resolved) but I can't find any info on the Ultramatch in this regard.

Does anyone know if you can use a Larue handguard with a Rainier Ultramatch upper?