Sorry, but not true, if it wouldnt hover with the 90 2 stroke that motor is shot. Here is vid of one hovering EASILY on a 91 saito
UCDSaito.91
ORIGINAL: tailspnr
You wont get a UCD to hang on the prop with a 90 fourstroker. I just flew a UCD two days ago with a OS90FX and it barely hovered at WOT.