I've been into older automobiles for several decades. Most of the original fuel pumps are a diaphram type that suck fuel from the tank. Whenever these automobiles are upgraded for daily usage in today's environment, a modern electric fuel pump is usually mounted externally, right near to the tank.

This enhances the fuel system's reliability, and because the fuel is consistantly pressurised and pushed towards the carbs, the engine runs smother with less fluctuations. Fuel vapour lock is reduced and fuel densities altered by temperatures, have less of an operational affect. 

It should be a simple matter to install an auxilliary electric pump near to your tank. The OEM pump can be left undisturbed. The electric pump could be powered directly from the generator when it's running, with a battery powered, momentary action, override switch installed to prime the carb for starting.

Pumps are much more efficient pushing a fluid, than trying to create a vacuum to pull the fliud. You also lessen the chance of loosing a prime on a vertical lift. Many pumps are adjustable for usage with float carburators, with pressures ranging from 4 - 7 PSI. They are available at most auto parts stores, or many sources on the internet.

My memory is a bit foggy, but in school I think I was instructed that a head pressure of one pound was realised with a 39" lift. If that is in fact true, a 7' height would take a pressure of about ~2 1/4 lbs to overcome. Most modern low pressure pumps have built in regulators with a high limit of 4-7 lbs depending on the model and manuf. If you need 3 psi for the carb, and ~ 2 1/4 psi for the lift, this should be within the range of the pump.

High pressure pumps used on fuel injection systems can sometime put out as much as 75 psi, and are often regulated to 39 PSI. You may not need a seperate fuel pressure regulator. Install the LP pump and see how the carb's needle and seat react. If it properly maintains the float bowl fuel level and doesn't overfill, you should be good to go. I typically run a 7 psi pump on a 4 lb system with no modifications.

Haven't heard that one before....

Man, there's a bunch of em mounted up there (ours, is in the rear tack with tank in the manger...no vertical lift),.... not saying it is legal, or not..........don't know..........but would like to know.......is your husband somehow in a field that would have the scoop on this?  This is very interesting, some of my good friends have some very very nice trailers with preofessionally mounted gensets up top, and I am appalled if it could get them into trouble like with the DOT or somebody...

I absolutely love having my gen on the roof.  Wouldn't want it any where else.  Gets the heat and exhaust away from me and my horses.  I don't really see what the problem would be with where it is mounted.  I had one in a different trailer mounted in the mid tack and was concerned about the heat the unit made.  It was an onan too.  Propane though and I didn't have a minutes trouble out of it.  Probably only used it 100 hours in 3 years.  The way I see it the dealer is the responsible party.  They installed it and the fuel tank and if it were illegal I am sure that they wouldn't have done it.  The biggest down fall to having it on the roof is that you have to service it off a ladder.  I have a friend with a 4star his is mounted in the manager and he has trouble venting the heat when he uses his.

Over the road reefer units are mounted at the top of trailer with their fuel tank mounted under the frame.  How is this any different?  I don't understand the issue.  Elighten me. 

My gen setup is very similar to the follwing:

http://www.horsetrailerworld.com/home/trailerdetail.asp?ID=191426

A second, elevated, smaller tank would require additional involvement to work properly. It would include extra plumbing as well as the tank. To fill the smaller tank from a large one, would preclude constant monitoring, so as not to overfill the top tank. Spilled fuel on top of the trailer would be very dangerous. The smaller tank would shorten the run times, and it would have to be refilled more often. A quantity guage would be necessary, with a remote sending unit and a placement that could be read from the ground level. This system would also have to use two fuel pumps.

It would be much easier to use the existing plumbing, and add an in line pressure pump.

Uncle Rube certainly has been around for a long time. He's responsible for learning to start fire, was the first person to eat a lobster, showed the builders how to get a large stone on the top of the pyramids, initiated the industrial revolution, and last I heard, told Al Gore how to start the internet.

Amazing man that Rube. Civilisation would not be the same without him.