Thanks! there is no particular reason for using 70mm fan. I am probably getting up to 50-55K RPMs. There are other examples of VTOL edf other than AVID's EDF-8 using vanes for all 3 axis. They are nice and not in the same category as Mono-Phan. Mono-Phan 5 is on drawing board. I already increased the flight time with new battery, ESC combinations. After I complete the adaptation of Multiwii, I will revisit different different wing designs for a better performance.