[Barnsnake]

Are you sure you really have a problem? If the system is completely filled with coolant when cold, it should push some coolant to the recovery tank when fully up to temperature. It should then draw it back into the system when it cools. I assume the cap has a functional draw-back valve and the recovery tank is plumbed to the bottom or has a dip tube all the way to the bottom.

Pressure should be pretty much equally distributed within the closed system and not spiking at a point of high flow. A possible exception might exist if you are getting steam pockets in the heads. Do you have a thermostat bypass hose in place? Even the three oversized holes you have in the thermostat don't really equate to a bypass. The bypass allows pretty much full circulation within the engine with the thermostat closed. The holes allow a "creeping" circulation throughout the whole system.