Actually, it doesn't affirm a dual residency at all. Dual residency meaning that you are a resident of two states at any one particular time. What it states is that for the time that you are living at one house or another you are considered a resident of that particular state, for matters concerning NFA weapons. This is the part that pertains to the arguement, it goes on to state that you may purchase a firearm at both residences. It says nothing about disposing of the firearms left at the previous residence, which for the purposes of the NFA you are no longer a resident of that particular state. Therefore, if you did what the BATF suggests in this letter you would simultaneously own NFA firearms in two different states, while for the purposes of the NFA you would only be a resident in one. The same thing as leaving them in a safety deposit box when you move to another state which is what this whole thing is about.
Regarding the unwarranted searches of a corp. which owns NFA weapons, this is just completely false. I suggest you do a search of the United States Code in the section pertaining to the NFA until you find a statute which addresses the aformentioned subject. Once you find the correct section look for the area where it discusses the loss of the right to unwarranted searches and seizures of corporate property once NFA weapons are aquired by the said company. Here is a hint...you will be looking for a long time, because you won't find it. Corporations do in fact have rights, just not rights like a person would have. They are considered an entity in and of themselves which is why they are allowed to purchase NFA weapons.
The only thing even close to what you suggest is the unnotified compliance inspection that the BATF is allowed to conduct on type 01 FFL holders. Even then the inspection must be conducted during business hours and I believe that it is limited to one but no more than two a year. They are allowed to conduct more inspections, but the license holder must me notified beforehand and is told the exact date and time when the inspection is to occur.
Many people also believe that this is true for type 03 FFL holders (of which I am one) and this is completely false as well. If at anytime the BATF wishes to inspect the weapons in my bound book I must first be notified and I then have the option of the BATF inspectors comming out or I may opt to bring my bound book and all firearms contained in it to the closest BATF field office to my location.
I have seen these exact two questions asked many times at subguns.com and these are the two answers given every time. Many times James Bardwell, a well know and very well respected firearms attorney, will answer them himself. If you don't believe me, just go to subguns and ask yourself, as I have seen chetchat has already done. A thousand posters over there that are much better versed in NFA laws than I am will quickly point you in the right direction. Also, Im not trying to sound pompus or rude, but if the dealer that you work for answers these questions any different than I did then he is wrong. If he isn't sure, then he will have something to ask the BATF inspectors the next time a compliance inspection rolls around.