The thing to remember is that unless your trust is totally jacked up, IT WILL BE JUST FINE.
Take the collection of different responses here - some have this in it, some have that. Some reference NFA, others do not. Some are el chepo Interweb downloads, others were written by the Johnny Cochran Law Firm for $16,000.
Each and every valid trust works just fine. I've used one for four different NFA items and it neither references "NFA" or "Revocation" anywhere in it. My father and brother-in-law are attorneys and they said it was irrelevant - and guess what? Surprise, it is irrelevant. A valid trust is a trust, period.
Do what you wish but don't take the word of ARFCOM basement lawyers as fact - any trust valid and properly executed in your state will be approved.
Choose an industry partner here or someone that's been used many times and you're going to be fine.