John, I'm flying my roo with a p-80 that its 19lb. My friend is flying his rookie with same engine as I. Other pal is flying another roo with amt-180 with 18lb. I belive that someone here post a thread about a rookie with a P-60 wich have less thrust than the SJ-1200.
Conduct a search and you will find more info. For me you shouldn't have any problems with that combination, just keep her ligth.