Yes ya just thread the hub onto the shaft.Yes its ok if there aluminum.They will hold up fine if there T6 but i dont know about the other kinds of aluminum cause i only use T6.And yes you can use a single bolt in the center.I would use a 5/16thsx18 NC.Course threads hold better in aluminum than fine.The only reason or 2 i did the 6-bolt hub was for a WWI plane and i had just purchased my lathe and i was trying out it and my new drill press to see how everything was alighned and checked for runout.Plus it just looks cool on a small echo engine.You could also use a piece of all thread or a stud and then use a nut like on a glow engine.