So, the permanent Kammback is now mounted on the car and I did a few other minor tweaks.
1) Taped the hood/bumper gap. It's actually a fairly significant opening on the Metro, as you can see in this pic:
That gap is maybe 24 square inches. Running at around 50 mph on level roads, my coolant temp was sitting at 198-202 F with that gap taped up, which is a couple degrees higher than with it open. This car's fan kicks on automatically at 205 or 206 F, and off again at 195.
2) Deleted the exterior antenna from the A pillar. Just like Mullet did to his car. Taped over the opening for now.
3) Removed windshield wipers (beautiful day, not a cloud in the sky)
I'm seeing some pretty nice numbers at speeds I haven't seen before. Just did a 60 mile round trip on secondary roads 38 mph avg/59 mph max, driving with load on the open road where traffic permitted (pulling over, or speeding up where it didn't). EOC and P&G at either end where appropriate and saw 80 mpg (US) even for the round trip.
On one 7.7 mile stretch of mostly level road, in a flow of traffic (NOT drafting) with an 8 kt following wind, I saw 75.8 mpg averaging 52 mph/59 mph max.
I'm not saying these three mods are particularly significant or made a noticeable difference, but those are numbers I'll happily take!