Trying to improve tracking in both level- and inverted flight, while bearing in mind the hypothesis after which boundary layer behavior may be be influenced by motor vibrations (or the lack of it), I have recently installed zig zag turbolators spanwise at 35% chord of the wing. I have chosen to put the turbulators at 35% chord in order to trigger layer separation at a defined point in level flight, rather then trying to influence separation at high AoA situations in manoeuvres.
Relevant airplane data is: 693 sq in. 65 oz electric pusher 5.35 sec/lap 19% trivial pursuit airfoil with smaller nose radius, flat plate flaps with round TE. Turbulator is 0.3 in wide and 20 thou thick, 20 in long, self adhesive.
With no trim change whatsoever, some 10 flights at zero wind conditions seem to indicate slightly better tracking without any side effect. Power consumption and behavior in manoeuvres remain unchanged. Inasmuch the effect observed is real or perhaps some kind of wishful thinking (placebo effect, perhaps) I do not know yet...
rgds, Peter Germann