hello, i am planning on getting a draco and want to put an underfold on it, i know that makes it a SBR and paper work has to be filed beforehand. i know about the tax stamp of 200 bucks but here is my main question. do i file the paper work, and as soon as its approved i can add the underfolder myself? after its all aproved am I allwoed to make the changes? whats the procedure here? ty.