I have to plead ignorance of the specific definition of "Reid Vapor Pressure" - I don't know how they define that term, whether it is a true absolute vapor pressure at ambient temperature, or a pressure differential from ambient pressure at ambient temperature, etc etc.
Having said that, vapor pressure is driven by two factors - volatility and temperature. Gasoline is a mix of hydrocarbon components with different volatilities (boiling points). As the temp of the fuel increases, the components of the fuel with the lowest boiling points naturally want to vaporize and come out of the liquid state. At the molecular level, molecules of this component are constantly flying out of the liquid state and into the gas state, and vice versa. At some point you get an equal number of molecules joining back into the liquid as you have leaving it, and you've reached equilibrium at that temperature. The pressure of the vapor of that particular molecule is what we call "vapor pressure", and it is specific to that component, and at that temperature.
For fuels with multiple chemical components, each contributes slightly to the total vapor pressure. When this vapor pressure reaches (or exceeds) the pressure that the fuel is under (whether that's ambient or pressurized, doesn't matter) the fuel will be at it's boiling point and you will have a vapor bubble form in the fuel line or fuel container. Pumps don't "do" vapor very well, so this results in what we call vapor lock - the pump loses it's prime.
In aircraft (and cars) the most common source of vapor lock is heating the fuel. This can happen from heat soaking a carburetor on top of the engine block at shutdown (resulting in the famous "hot start" issue), or any other situation where the fuel picks up enough heat from ANY source to raise it's vapor pressure to the point where it is equal or greater than the fuel pressure. At this point you have fuel vapor, not fuel liquid, and you have a problem. Mechanical fuel pumps on the engine block operate at an elevated temperature due to heat soak from the engine, and they transfer this heat to the fuel flowing through the pump - you are essentially "cooling" the pump with fuel. When the fuel is flowing fast enough (full throttle or a good portion of it), the mass flow is high enough that the temperature increase in the fuel is not of much concern. The problem comes when you close the throttle (very low fuel flow) for a few minutes (think descent into pattern altitude from cruise), and then the same fuel quantity is exposed to the hot pump for a much longer period of time, raising its temperature to a point where it can easily result in vapor lock.
To totally avoid vapor lock, all you have to do (techically speaking) is keep the fuel pressure higher than it's maximum possible vapor pressure. You can accomplish that either by keeping the fuel pressure high, or the temperature low, or both. You could certainly pressurize the tanks, but you'll have more issues with leaks and stress on rivet lines that it is worth. Any type of pump arrangement that will increase the pressure of the fuel will raise the temperature the fuel is able to achieve without boiling - and any type of cooling or insulation in the FWF area will reduce the amount of pressure required in the fuel system to keep the fuel from boiling. Electric pumps are convenient because you can place them aft of the heat source (pulling cool fuel from the tank) and pressurize it all the way forward - at that point, you don't worry about fuel temps except under extreme circumstances with a carbed engine. An injected engine will operate at high enough fuel pressures that you won't see vapor bubbles in the pressurized fuel line, even under extended heat soak conditions. The primary function of a fuel "boost pump" on an aircraft is to temporarily increase the fuel pressure leading to the engine-driven fuel pump, this collapses the vapor bubble and allows the engine-driven pump to catch it's prime again, and continue pumping. If that hot fuel is driven out of the pump area before the boost pump is shut off, then you're good to go. If you shut off the boost pump while there is still hot fuel in the area of the engine-driven pump, you'll go right back into vapor lock as soon as the fuel pressure drops, as the fuel will immediately boil again at that point.
