We have extremely low damage from our MacNeil top brushes, maybe 1 or 2% of all claims. Mitter curtains grab rear wiper blades so you have to bag them, not with a top brush.
As far as MacNeil top brush retract, we used in our first location the MacNeil 4500, MacNeil now recommends using a Kesseltronics r.TC to control their equipment, and we have been more than happy with the r.TC. Most controllers should be able to control them.
There is no sonar problem with a wire dog cage, properly installed after market roof racks are no problem. Pickup racks depend on the type, but as a whole we reject only a very small number of roof racks that come through.
Don't count on a top brush being the cure for bugs. If bugs are left to dry for a couple of days, it takes some extra effort to remove them, even with 2 top brushes. We have and are
training our customers to come in right after a road trip. Wish they would mind us!