I just looked into doing this myself for a twin.
First of all you can use a twin sync from wike electronics to sync two motors, if one cuts out it drops the other to idle.
http://www.troybuiltmodels.com/items/WRCTWINSYNC.html

As for running a rc engine in reverse, Jedijody ran a dle 30 in reverse but said it had to be set a lot ritcher.
The dle 20 has a timing bump which alters at a certain rev, they may be a bit of a problem to use in a twin but if they are syncronised it could be ok.
Everyone I spoke to said in model application you didn't need to worry about making them opposite rotating,
I emailed EME they said it's ok to change the reed switch/hall sensor location and run it backwards, not sure if I'll worry about it though.
I was going to use the EME35 in mine as they have an onboard electric start for their 55 and 60cc,(which also fits dle 55 and DA50) they will have it for the 35 in a few months I'm told.
http://www.sdshobby.net/special-electric-starter-with-johnson-550a-brushed-motor-for-dle55-eme55-eme55ii-eme60-gas-engine-p-11462.html
That would be pretty cool, sitting at the flight line, start one engine up via the tx, then the next, taxi and take off, nice and scale

quote:

ORIGINAL: All Day Dan

dleclaire, don’t overlook the fact that you will have to use a crankshaft with opposite threads to avoid having the prop coming loose. Dan.

quote:

Interestingly, the "prototye" P-38, the XP-38, had inwardly-rotating engines (before it crashed). However, all subsequent P-38's (including the first batch of YP-38's) had outwardly rotating propellers; Warren M. Bodie, in his book The Lockheed P-38 Lightning: The Definitive Story Of Lockheed's P-38 Fighter, states that, "Engine rotation was changed so that the propellers rotated outboard (at the top), thereby eliminating or at least reducing the downwash onto the wing centersection/fuselage juncture. There was, by then, no doubt that the disturbed airflow, trapped between the two booms, was having an adverse effect on the horizontal stabilizer. No problem was encountered in reversing propeller rotation direction; they merely had to interchange the left and right engines."

quote:

In designing the Lockheed P-38 Lightning, the decision was made to reverse the counter-rotation such that the "tops" of the propeller arcs move outwards, away from each other. Tests on the initial XP-38 prototype demonstrated greater accuracy in gunnery with the unusual configuration. The counter-rotating powerplants of the German World War II Henschel Hs 129 ground attack aircraft, Heinkel He 177 heavy bomber and Messerschmitt Me 323 transport used the same rotational "sense" as the production P-38 did.

The following aircraft have counter-rotating propellers:

Single engine, chain driven propellers :

• The Wright Flyer

Twin-engine, one engine per wing :

• de Havilland Hornet
• Lockheed P-38 Lightning
• Heinkel He 177 Greif (fourth prototype onwards)
• Henschel Hs 129
• Piper PA-31 Navajo
• Piper PA-34 Seneca
• Piper PA-39 Twin Comanche C/R
• Piper PA-40 Arapaho
• Piper PA-44 Seminole
• Cessna T303 Crusader
• Beechcraft 76 Duchess
• Piaggio P.180 Avanti

At least four engines, two or more on each wing :

• Messerschmitt Me 323 Gigant transport
• Airbus A400M Atlas - first aircraft with propellers in counter-rotating pairs on each wing