I was one of the first people to do it on the Reliant back in 2001. I found at the power level the car was at the stock returns were not enough.
After fabricating a 3/4" flowpath from the SOHC valve cover to where a block off plate would be oil in the catch tank dropped off to almost nothing, a teaspoon in a single seaon. TIII has the same returns, the oil has to work pretty hard to get back to the pan with the pistons churning up the airspace in the crankcase.
Gary