Prototyping the wheel covers today.
Worked out the zip tie locations on the narrowest part of the spokes.
Punched out the holes with a screw driver. Doing this instead of drilling curves the edges inward so there's nothing sharp to rub on the tie.
Immediately I discovered that the ties have to be very tight else the cover will rattle. They also do move around a bit resulting in a slightly noticeable imbalance going down the highway. I'm going to drill the hole for the valve access and then prime and plasti-dip them. My hope is that the traction from the rubber will hold them in place so they not only don't slide but don't have to be zip tied so strongly. If they still move around I'll try adding a peg to the cover that extends down into the opening for the wheel center cap.
On a 10 mi or so jog down the highway I was bouncing around 56 mpg by the time I got off. Not sure how much I trust that tho. I filled up the tank today and came in at 38.6. Lower than my last fill. Doesn't make sense as I've been doing plenty of P&G and coasting in neutral, cruising in 5th unless I need some power. And the last fill at 39 mpg was only half hypermiling. Maybe I should stop buying Costco gas.