Heres a pic of my FS46 stihl.APC17x8 at 7400.Used engine i bought off a dealer.28cc[27.2cc actual].I also have the 26cc[25.9cc actual].This is suppose to be better because it comes from a pro version of weedie.Look up stihl in the search bar on the bottom right hand side of the page.Look in this forum only.Youll notice in the pic it can be rail mounted or mounted by the 3 lugs on back of engine.it comes this way stock.I did one of the weedwacker ones your talking about but i sold it as it wasnt worth it to me.Like aviator said,they will work on a high wing,or biplane as long as its light.