Hi Neil. Reading through this thread many months ago convinced me to get moon style hubcaps and try a grille-block. I saw some modest gains though admittedly I still push 75-80 mph up and down I-5 (San Francisco/Portland) which keeps me in the mid to high 30's mpg. I now have an Ultragauge and a renewed desire to increase my efficiency, so I returned couple of nights ago to check your progress. 50+ mpg is inspiring!
I've got a a few questions – and please forgive me if the pertinent details have already been mentioned. I read the entire thread at 1a.
1) I was thinking of getting some alloy wheels until I read that you noticed no loss of efficiency when you switched to steel. Are you still rolling on steels?
2) What thickness of Coroplast are you using?
3) IIRC, you removed one face (plus corrugations I assume) of some of the pieces of Coroplast. Which pieces were those? I'm assuming not the wheel skirts because of the need to insert the metal rod, but perhaps you stripped away some of the back of the wheel skirts?
In any case, thanks for detailing your efforts. I hope to emulate some of them and save a little gas
Hope your EV project is going well