I hope these pics will make sense to you. If you join your outer star pieces like this the joining of the rosettes will be easier, more straight line less fussy tight points. With this joining method it is easier on the brain if all your stars are the same fabric, but w/ a little planning a the sacrifice of some brain cells you can do it w/ different star points.
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See how the star points are joined in units to the diamonds and small pentes
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The drawn in lines show how much straighter the joining line for the rosettes are and how your not putzing w/ the really tight star point turn.