splitter

I'm also interested in how people have their splitters set up - I have an old shape SR3 that has been upgraded with high downforce aero package. For info I have set the splitter so that the top surface is horizontal, with the shape of the underside of the splitter this makes the underside higher at the leading edge than the trailing edge. Not sure if this is 'right' but car feels fairly well balanced so I'll only play with it if someone here with experience in this setup has some advice! I've attached a photo that isn't great but gives you an idea of what I mean.

I believe the answer is yes, and I set my front diffuser height such that it has a clearance of 45mm front and rear.  That said, I do not think it is critical because I have run it with the front edge higher than the rear which did not affect traction or handling balance.  On the SR3s that I have owned (2015 to 2021), there are two stays on each side.  The forward stay adjusts the height of the front, and the side stay adjusts the height of the rear.  Each stay has an adjustment coupler with left and right hand threads and a jam nut.  To adjust, loosen both jam nuts, and then turn the coupler.  Note that jam nut with left hand threads loosen the "opposite" direction.

A couple notes.  The car is meant to be set up per the factory chassis setup specifications.  It requires special equipment and knowledge to do this, and it is best to seek a race team or Radical dealer to do this.  It is particularly important to set the rake to factory specs.  The rake (difference between the front and rear ride heights) impacts the balance of traction between the front and rear wheels.  Also important are the corner weights and the other setup adjustments.  After the chassis setup is completed, then one would set the clearance of the diffuser. 

It is not as easy to measure the clearance of the diffuser to the ground plane as one might think because it is difficult to find a truly flat surface.  At Radical Cup races for example, there is a minimum height of 40mm, but we have found that the exact position of the car affects the clearance.  Rolling the car forward or backward a few inches shows that the clearance measurement changes, sometimes significantly, which means that the road surface is not uniformly flat.  This is also typical of any concrete surface.

I have observed that some cars are engineered to have the front diffuser with much higher front edge than the rear.  For example Elan DPO2 that race in SCCA P1 class, which have been re-engineered by race teams and highly modified for increased downforce.  The modified front diffuser is turned upward aggressively which I imagine directs more air under the chassis than the original configuration.  I don't understand aerodynamics, but I am told that what happens under the chassis is just as important as what happens above.  The picture below of Chip Romer's DPO2 shows the front diffuser modification.  I have seen other DP02s, with even greater clearance in the front edge.  

Last note, and this is not really part of the original question -- I will only attach the downplanes in wet conditions on my SR3.  This is typical for most tracks and most racers because the car has sufficient downforce without the diveplanes.   The SR3 has a disadvantage of drag at high speed, so we tend to trim out that drag in the front and rear to achieve greater speeds in the straights.  The SR10s on the other hand have sufficient power and additional weight, so racers typically keep the diveplanes attached.