If you want to hover a 6 lbs. plane, get a YS 63, Saito 91, Magnum 91, or OS 91 four stroke. However, the Saito 72 might be able to do the job for being light. As stated above, you want an engine that can swing a large diameter, low pitch prop. If you use the Saito 72 to spin an APC 14x5 prop at 9300 rpm, then according to Thrust Calculator, this combo would give you 9.97 lbs of static thrust.