You guys can go on cutting into tanks that had fuel in them
- but -
Years ago at my local junk yard there was a car that had been there for at least 5 years with the inspection cover and the filler hose on the top of the gas tank removed. There was no liquid fuel in the tank because the guys in the junk yard siphon the gas out of the junk cars to run the vehicles they use in the yard..
One of the workers was using the flame wrench to cut some metal loose under the tank and he accidentally cut into the tank which EXPLODED! He survived but it wasn't pretty. I would imagine that the heat caused the sludge or varnish in the tank to vaporize and the fumes exploded.
About the in-line pumps overheating, originally I was using a MSD #2225, 125#/" max, 43gal/hr, 7 Amp fuel pump which had enough GPH flow to run a Nascar engine. As other people have described it was -very- noisy. I also have an internal pump from a Mazda MPV which I thought I might use.
Here is a comparison of the Suzuki GSXR pump to the MPV pump. The MSD is even larger than the MPV pump.
The point of all this is that while the fuel will cool the pump I don't think the lack of fuel is the only reason why an external pump might overheat. The typical 12V charging system is set for ~14.1V. If you are drawing 5 or 6 amps because of high fuel flow and/or a high pressure setting the pump is dissipating 70 to 84 watts of heat (of course some of the input amps are used to pump the fuel). The fuel will carry some of the heat away but the typical external pump I've seen is usually not out in the air stream so it has limited external cooling. Over a period of time the high heat can damage the motor windings if they aren't made with high temperature insulation. Even the motor on my electric water pump is rated at a lower temperature than the coolant it is pumping!
As Miatav8 et. al. pointed out ..........
Many (most?) of the accessory "high output" pumps are very overrated for most of our use considering that we run 12 or less gallon gas tanks on normal roads. Does your engine really require a pump that can empty the tank in 15 minutes? If the stock pump ran a car that weighed more than twice the typical Locost weight it should run a Locost.
The Suzuki flow test (minimum) is only 1.2 gal/hour. The adapter might have a restriction to cause some fuel pressure to exist.
Also, I'm pretty sure the pressure regulator on the internal pumps is set to a higher pressure than the one that is usually mounted on the engine fuel rail. In affect the internal regulator is a safety dump valve.