My RotoFly is marginal here in Boulder at 5400. As said before, you need the power and blades. I run over sized blades on my nitro machines, so far I have all the power I need. As for a small electric, I'd suggest you go with a 400 class, like a trex and make sure you put a good motor on like the scorpion 2221-8, and a good pack to deliver the power.

If you are looking for an indoor flyer, I don't think you'll find one off the shelf with enough power at all, or able to handle an upgraded motor.