Hi Stewart,
First.... thanks for getting me started on using olive oil, it has been a great success.

George,
I made different fuel mixes using 10% ether. They had about 8% castor oil included.

Mix No1 had modified olive oil at about 25% added
Mix No2 had a car diesel engine semi synthetic oil added at about 25%

Both mixes had about 2% of ignition improver added (it's actually sold for use in diesel cars and trucks)

Both mixes ran well but needed a couple of primes of normal commercial fuel down the venturi and then a spin with my starter motor.

The mix with olive oil, as the main part of the lubricant, would allow the engine to idle very slowly and extremely steadily. I left it idling for 4 minutes at a time. It would accelerate O.K but there was a bit of hesitation.

The mix with car oil, as the main part of the lubricant, would idle O.K, not quite as slowly and steadily as the other mix though. The throttle could be thrust open, by hand, and the response was both instant and smooth.

Then I had an idea (that's rare ! ) I mixed both fuels so I had 50% of each. This mix when tried not only gave the very slow idle but would respond instantly and smoothly to thrusting the throttle open. This series of tests took up 2 hours on the day I did it. I repeated each run with a particular fuel at least 3 times in order to check that results were consistent.

I believe you also intend to use diesel with gliders. I find that my engines work hard to get my 100" gliders aloft and then will be at idle for long periods, especially if there is decent thermal activity.
I have found no throttling problems when using my fuel mix in this way. Once the good thermal passes and the heavy sink appears it is nice to have the engine wake up when required

For priming I just put 2 small drops in the venturi. You may need to do this a couple of times before the engine will ignite the low ether content fuel. Fuel with no ether at all can also be started in this way but will take, maybe 3 or 4 primes before there is enough heat to ignite the fuel.

To start with I would be inclined to use either 20% ether, like Stewart does, or use at least 15% ether. This makes for easier starting. A mix of castor oil and modified olive oil will probably do the job for you. The castor gives some margin of safety and the olive oil should keep things easier to clean.

The other thing I do.... my engines are on "power pods" which are held on by rubber bands. I fit an exhaust deflector (as used for glow engine) and then stick a length of brass (or aluminium) pipe into the exhaust deflector. The other end of the brass tube is pointed down below the fuselage and is held in place by one of the rubber bands. This makes the exhaust quieter and also deflects most of it away from the glider, alternatively you could run a tube right to the back end and keep the glider even cleaner ! The diesel engine is not as sensitive to back pressure as the glow engine.