If you can get it into the country in a single piece, that is fine and it can be left un two toned.but customs will NOT let it thru, so it has to be cleverly smuggled - Illegal
If you split it into two parts, when you get it back here and assemble it it couts as 'manufacturing a RIF' - Illegal
two tone it AND split it if I were you.
Luggage scanners and things can easily detect anything (they even see clothes). Even plastic knives and porcelin guns show up bright as day. Most airports have computer software to assist in the scanning. Unless it was fully declared I wouldn't bother. It'd probably be spotted with you trying to leave the country because the plastic/fibreglass parts show up just as clear as the metal, disassembling won't do a whole lot.
Then there's the bloody-mindedness of most officials towards RIFs that you have to remember. It's like the Psueodophoto arguement, the fact its not real doesn't alter the way the law see's it. In law, these things count the same as real. In some juristictions - especially the US I believe - an imitation firearm is the same as a real one. If they wanted to make trouble, it'd be pretty bad.
As for what they happily confiscate, the list of things you're allowed on a plane, either in luggage or hand-luggage, is pretty ###### small. I got taken off a plane in Amsterdam because I had a short length of nylon rope (don't ask) in my suitcase. They didn't care why or want to ask about it, they just took me off the plane to show me they'd removed it after seeing it on the scanner. Making me miss my flight was essentially the unofficial punishment to make sure I 'didn't do it again'.
It depends where you're flying from in the US, their security is pretty hit-and-miss but I personally would not bother. Two-toned and disassembled probably won't change it one iota unless its fully declared, you get a slip from the airline saying they're happy to carry it AND that its not a violation of the AIRPORT rules carrying it through their infrastructure.
Edit: The word filter scrambled the word damned?
