Ok, Thanks Boris.
Those HK motor mounts work but aren't very good on the M4 booms. I have a couple flying fine with them but one of them I had to add a brace between the motor and shaft to get it to fly smoothly.
I have flown many off the booms at about 90mm and they fly fine. You will find if you get the motor prop A1 A2 numbers and do the Quatos calculations for the frame it will fly much better. It fly's better at first because you have a real IMU and a real radio controlling it and with Quatos compensating for what's wrong. I would venture to say now you have a great flying toy, you can make it a great flying multi rotor.
I asked the question also to see if the boomed version is going to be popular enough to justify the extra cost to make.