Was talking with an "F" owner today, he claimed that the Lasar cowl enclosure for the A-G models doesn't produce the 4-6 knots improvement that it claims to. Is there any truth to this? if so, how many other Lasar speed mods don't produce the gains that they claim? Another thing, have Mooney engineers ever heard of these fasteners called flush rivets?? It seems to me you could pick up at least a few knots by using them. Or do they not make much difference??