I checked out rc universe review of the UCD and he has a tru turn all right but is using the 15 X 6 prop so it doesn't answer the question. I have emailed tru turn with the porblem and await their answer. Will post it if interested as this has probably come up or will come up again. I would like to find an aliminum washer or spacer with the right id and od so as not to ad weight to the nose. That would be one solution. The other is to go back to the "Rudolf the red nose spinner" that came with the arf and put the 16 X 4W on with the stock YS 91 washer and nut and hope there is enough thread.