I decided to try this..thinking back to a dodge omni of the 80s. the omni refused to ride smooth without the nubs of axles covered... The sube has four dangling, and it shakes randomly, drivin me nuts. So, I spent too much for a hole-saw bit at 3inch, and hacked up some high grade aluminum, and made a self centering steel backing.
By high grade, I mean the drill gun was smoking by the timje I worked it thorugh each piece...
I then proceeded to fly down the highway...sure enough, hunch proved good. Smooth...and that equals fuel.
I cannot do the disc stuff I have seen here, but this highly heatsinkable self center is over 4 inches...similar purpose and result I presume.