Westy
I thought about fitting similar flaps to the wife's Cat but by the time I got around to it the stonechips beneath the carbon wing protectors had removed the white paint - the fibreglass gel underneath is black so kinda matches the CF wing protectors so i never bothered with the flaps. Many Caterhams have a clear plastic film applied over the bodywork paint to prevent these stonechips, but this really needs applying immediately after the car is painted.
It's surprising how much damage the stonechips do to the painted rear wings. The clams on my S4 prevent this, so I guess that's a plus for the clams, the clams also prevent the passenger burning their leg on the hot silencer when getting in/out of the car, so a 2nd plus for clams

As far as front lift is concerned, well TBH I don't go fast enough, often enough to notice or worry about the front lift which is supposed to happen with clams, For road use not worth worrying about IMO.
If you check my PH Lotus 7 s4 thread there's plenty of pics of S4's fitted with cycle wings which again IMO don't suit an S4 - but other's will strongly dis-agree, what's not apparent is the body mould line which is hidden by the clams but visible when cycle wings are fitted to S4's and which looks odd IMO , clearly the S4 was designed for Clams
