I'm not next to my engines/planes right now but I've done a lot of toying around and mock mounting between the OS 61RF-P and YS-60/61 as well. Mainly I wanted to replace the OS on two of my classics with the YS, but it wasn't that easy to do so. The planes are the MK Aurora and Arrow, which both came setup with the OS mounted on the MK wood beams.
The problem is the YS uses shorter bolt spacing, and if you reuse the forward bolts, the spinner gap becomes too large. Also, you would have to re-drill for the rear bolts, but it is too close to the original holes. For the MK kits I have to somehow fill the original holes in the wood rails, and it'll be hard to drill straight as the drill will tend to slide.
BTW anyone know what material to use to fill the original holes on the wood mount? I've heard baking soda? I'll probably swap the whole setup with a MK soft mount, but curious how others solved this.
SuperViking, I'd love to buy one of the aluminum mounts for the YS-60/61. I'm completing an Atlanta with a YS-61 classic that could use it. How can I get one?
In general, what's the best rigid mount people have used for the big block .60s? Richard Verano said when he first mounted a YS on a cheap Hangar 9 nylon mount for the P7, it vibrated so much it took a lot of power away. He had to change to a better a mount to get the power back. What about the Dave Brown glass filled nylon mounts? What engine mounts do you guys use?