I installed 2 beams for cs10 to fasten to them. It was only a test really to see if 70mm fan worked, if it was no good i was going to install a cs12 fan and motor, but it has worked well.Model is light and powerful, and has a lighter wing loading, bonus all round i would say.
For 3 yrs, I flew an RBC Panther on a 70mm Minifan. First with a 4s ARC 28-48-1 system for 1400W, 4s-4000 Zippy and 4.3#. Thats about 2# lighter than the 90mm versions.
Later, I switched to an ARC 28-48-1.5, 5s Zippy 3000, for 1200W and 4#. Even better performance and an amp draw of 60A vs 105A.
Now I'm looking for another kit for the CS rotor and alloy shroud with BL32 on 5s-6s. There are many 90mm designs that will fly just as good or better than the intended 90mm, due to less AUW and sometimes higher watts and efflux than the original was designed.