depends on state and individual b/d's... the big problem comes inot play more on the nasd side; most staes ans b/d's wont allow you to be dual registered, particularly if you are being paid commisions from both...
the answer ultimately will come from your compliance officer, so when you present it do it in a manner that doesnt spook them and clearly show there are no conflicts of interest.
when i did it i presented my prop firm as more or less just a trading account, etc... your compliance person at your trading firm should be more understanding so clear it with them first and ultimately it will help if you have both co's talk to ease teh others concerns, it will be better from a fellow co.
ive been through this before and succesfully did it so PM me if ou want to talk