If you really hate switching them around that much, why don't you just sell them and buy a 16gb flash drive. I am not trying to be a jerk here, I am being serious. It seems like you have put a lot of time into figuring out a way to get them to work at the same time so it seems this is pretty important to you. If it is then why not just sell them and buy a bigger single drive? The cost difference is not that much. I have an 8gb and a 16gb both are SanDisk's that I got at Walmart, and if I remember correctly the cost difference between them was only $25ish so with selling 2 used 8Gb ones you should be able to get pretty close to the cost of a 16Gb one. If it is not that big of a deal to you or the cost is more than the switching around is worth to you then just keep them, but if it were me I would just sell them and get a bigger drive, IMHO. Anyways I hope you know that I am just trying to help and not be a smartxxx here. Talk to you later.
Sincerely,
Elmoreas