Wild Bill,
Apart from fitting a full dry sump system the only other alternative is an Accusump, this is a cylinder that has a piston and spring in it. When the engine pressurises it pushes the piston down the cylinder against the spring, if there is a drop in pressure the spring forces oil back into the system. Simple & clever idea, Merlin sell them circa £200. They are popular with the K Elise boy`s.
I am surprised that you are noticing such rapid changes in oil pressure as the oil pressure sender is damped which normaly masks the problem, may be your sender is on its way out.
Stu,
I fail to see any beniftit in reducing the amount of oil that is pumped around the engine
Rob