Possible trip to Red Bull Air Race at Ascot and want to make sure I'm covered in terms of lens reach. I have Nikon DX and FX bodies and a AFS 70-200VRI. Would I be better buying or renting a TC (which one?) or a 300mm F4, or what else? I'm gaining an interest in nature/birding so the kit would get used regularly which is why I'm considering rent vs buy. Other use is occasional motorsports (previously I've rented a TC). I prefer to use the FX body.

