ORIGINAL: LNEWQBAN
I believe the problem with this set up is greater changes in the pressure that the carburetor sees for nose up and nose down attitudes.
For level flight, there is no problem beyond the added weight.
That would be true if fuel were compressable. Most liquids are not. It is the air ( or lack of it ) in the tanks which does this.
A properly plumbed system would incur no additional problems. e.g. plumb it like a Heli's header tank.
A header type plumbing arrangement, which is what should be used, only pressurizes or vents the very last tank in the chain.
So it is not much different from a pressure standpoint, from running a single tank.