Damn.. those olds wheel covers are exactly what i want for my car
Some great info here - thanks chaps.
I'm thinking of making my own covers, just a couple of them first. I can then try these out on front axle and rear axle separately to see which works best.
I had been thinking about just adding to rear (to leave fronts open for brake cooling) but based on those cfd flow images i think that's flawed - fronts look to be most benefit.