I destroyed a 3 blade fan using a high KV motor on 4S. I think the revs were just to much for a cheap fan.

Yes more cells and the higher voltage available will mean (if used) higher amp draw. Always stay within the max C rating of your cells unless you want to shorten their life by an alarming factor. See the FMA direct site for white papers on this if you are interested.

I flew with the cones and did get a bit higher speed but the vertical did suffer. You can make up more robust cones from X-ray film or overhead transparency material. I personally want good vertical so fly without at the moment. The (small frontal ram effect) inlet ducts and overall drag of the F-15 airframe are limiting factors. If you want to go faster get something with better ducting and more powerful fan potential or a bungee/no wheels job. This is just a parkflyer foamie don't forget! The retracts sold it to me. Great fun.

My 2c
Patrick