Hybird 46 mounting

I have a hybird 46 in NFA jail. Looking at getting all the attachments ready, My scorpion has the original m18-1 threads. I know i can get it rethreaded but the gunsmith local to me is recommending against it because he says it would make the barrels walls really thin. What are your thoughts on this? Or with the silencerco AC690 adapter just be easier to use?