Some day I would like to put 4 units together, 9 cylinders each, for a B-17.  The trick is getting the size just right for scale appearance.  The sound though, would be the icing on the cake, imagine a flyby of a scale B-17 that SOUNDED like a B-17.   We have a few 9 and 18 cylinder radials in the shop, would be cool to take one apart and miniaturize it.   I know it can be done as I have seen a couple 9 and 18 cylinder engines that run, but they were too large to be practical.