BuffDragon,
It's all about educating yourself. I spent almost 2 years learning about NFA and asking and reading A LOT before I purchased my 1st silencer. If you show confidence and a firm grasp that you know it's legal, you should not have a problem. If you act timid and act like you're hiding something IMHO that's when SHTF.
Every time I'm at the range I get someone asking if that's legal. I have had NFA101 at least 6 times over the past year. This is the only time it's been for LEO.
I say go for it, once you own NFA items the benefit's/joy far outweigh the other bullshit that goes along with it.
Tanlegsintx (my wife) can now confidently explain to folks and LEO with a reasonable degree of knowledge the in's and outs of the approval process and the legal requirements.
ETA: Most cans are IMHO are bought from a reputable manufacture with really nice rollmarks and machining. If you form1 a can and don't make it look "pretty" you might have to explain in a little more detail.
ETA2: I'm down with what RenegadeX said. I'll be sending in a letter on Monday.