I currently have 30mm of spacers with a 15mm one above the Aeon and 15mm one below. The suspension is lowered by around 10 to 15 mm and the gap at normal ride height to the Aeon spacer about 15mm and 60 mm at full droop with the limited droop Koni shocks from TTR. I am using 150 lb/in rear springs
For a road car the Aeons would come into play a little early I suspect with this set up, especially if you have softer springs hence I would try 20 mm of spacer. I have them top and bottom as they help protect the end of the Aeons from getting chewed up. I had a single 20mm spacer on the bottom of the Aeon a number of years ago when I was using 110lb/in rear springs and the car was more of a road car
Lots of variables so to some degree you need to experiment to find out what works for you with your car, tyres, other suspension variables and driving style. At one point i tried a stiffer Aeon as there are a couple of load ratings and Lotus used the softer one. But the stiffer one just gave to much of a spring rate transition when it came into play so I went back to the Lotus one
Picture at normal ride height below , hard to see as spring coil in the way but around 15mm gap from top of shock to spacer below Aeon
At full droop its a bit easier to see
The spacers I used are actually poly bushes. I just went through the catalogues from the makers until I found a suitable thickness and inside and outside diameter. The OD taper you see in the photos also fits nicely to the smaller diameter top of the shock and larger diameter bottom of the Aeon. Lotus used aluminium for the 20 mm cylindrical spacers they added on the later Plus 2 these has a small lip on the bottom that could be peened over to hold them onto the top of the shock so they did not rattle, they did however tend to chew up the bottom of the Aeon.
cheers
Rohan