You ought to have plenty of runway for what you want to build even without the prevailing winds...
An IMAC type model will require substantially less runway than a warbird due primarily to the differences in typical wing loading, so it will slow fly much better than a warbird. Your "overseer" may not be aware of that, he may be concerned about safety, or it's possible he just does have a bias.
With a sport aerobatic model you can either land it more like a full scale or what I call the IMAC landings, that is setup for slow flight and just set it down three point, either way when you go ahead and close the throttle to idle, those big props turning that slow will decelerate the model much more than you'll ever see when running glow engines. Most of the IMAC guys I've seen fly, as well as the two who are helping me, use that slow flight technique which has a rather steep approach angle, but a really short landing roll. I'm still working on how to do that consistently, but even without doing it that way I wouldn't be afraid of the runway length.
Now with your prevailing winds, it's a total non-issue IMHO...
