I have been doing more tests with E85 fuel and have some info that you might make use of. I bought a remote temperature meter from Harbor frieght on sale, with a laser pointer. I measured the cylinder head temperature of several engines in the .25 to .61 size range in cold weather (30 degrees to 50 degrees F). Engine manufacturers don't seem to give that info out. Engines running on 15% nitro commercial fuel seem to run between 350 and 400 degrees F. E85 runs at about 220-275 degrees F. (These of course are on the bench tests). I find that wrapping the cylinder head with thin cardboard to insulate it brings the temperature back up to 350 when using E85. This really helps improve the engine operation. Also after trying every glow plug I could get my hands on here in the out back, I have settled on the one that gives the best performance and life, at a reasonable cost (remember my goal is the cheapest flying possible). The Thunderbolt #115480 4 stroke and large 2 stroke glow plug is the best I have found. It runs very well on E85, with excellant power and has a long life from my tests to date. Note it is still winter here, so temperatures rarely go over 50 dregrees F, usually sub freezing. The OS F 4 stroke and other 4 stroke plugs are too fragile, and burn out after several flights. The cold plugs run, but the colder operating temperature retards the timing so output power is low under the cold conditions. Perhaps they will be better once summer arrives. The Thunderbolt plugs are available from Hobby People for $5.49.
I advise buying a remote sensing temperature meter frome Harbor Frieght or some other place, as it really helps figure out what is going on.
Once summer arrives, standard E85 will become available (85% ethanol, 15% gasoline). Hopefully it will work better than what I have now (70% ethanol, 30% gasoline, the winter blend available here).
My next step is to make some new cylinder heads that accept 2-3 glow plugs. I think that will boost the power. Only one plug has to have an intact coil, so I can use some of my sacrificed test plugs. I will make the heads with no cooling fins to increase the temperature up to 400 degrees F. I will make a baffle to install for winter flying as well. I would like to make an automatic temperature regulator baffle system using a servo and a small microprocessor controller, but it would be a bit heavy and only practical for larger engines. I will post any new test results that I find.

Good luck