I agree that mixing may not always work but there atre plenty of under attended AMA events and this would possibly spice things up a bit.
The thing that I don't understand is how would a post 76 plane cost more if the rules on engines were to stay the same.
Had to mention 1 other thing I remember the King Altar, the engines back then were underpowered for the big frame but I'll bet it's a great plane with a YS 91 on it.
Mike