Stefan, it takes at least 10psi to get the jets which are around .065-.070", to squirt across the width of the cylinder. This from Jim's and my experiments. 15 is really a better number to achieve. On Frankenstein, I would guess it's only just a dribble. There can't be too much pressure on that return line, it exits in a 1/4" hole in the tank, so there isn't much restriction to develop pressure in the return line.
I'm estimating the sporty return has about 2 times the pump capacity of the WL. However, keep in mind, the return line is only going to output what goes into the engine. And on a WL supply pump, that's 1/12th of a quart per minute. And it frothy to boot.
Now Frankie has never had any lubing problems, but keep in mind that it also has a 3 hole crankpin flinging oil as well as the skirt oilers. Also, I suspect as the K style heads and jugs have a different shaped combustion chamber, the heat issues are different as well.
In short, I wouldn't depend on standard WL pumps to output enough oil anywhere to keep a skirt oiler system operational.
You're going to have to boost output to get satisfactory operation.
Having said all that, remember, most of my flathead oiling experiments have been with the Big Twin, which is a far bigger motor than the 45, and may well have bigger problems than the 45.
By the way, I've posted the sporty conversion on the web, and have started another thread to reference it.