Billy prop size determines engine spacing. If you use a 10" max dia prop you will have the engines on the straight part of the leading edge with no taper. I use a 10x6 on my saito .30's. If I had the saito .40 I would consider 3 blade props. This way it would keep under the 10" size. I allowed 3/4" between prop tips and so far this has been ok. But be sure to check the prop to fuselage clearance.

Your angle for engine installation looks very much like what I used. I actually put the rear have of the nacell on the firewall then mounted the nacell to the wing with the wing vertical. I had previously marked the wing for c/l of each nacell. I adjusted the nacell to keep it straight and centered up the 4 engines on the wing.

Now lets finish up and go flying.

I have held off on building anything due to our field closing down. Currently we have at least 3 fields being closed in the next 90 days with the closest flying field about 45 miles away. So this really nixes flying unless we can find a field. We have had several leads and there has always been something to prevent us from using it.[&o]

Jim