Gotta have at least 6 cubic inches, for sure, Muff modded and some port work is what the pros do to their saws for Hedges, slotting the cam gear can get another whole HP of torque on the blades, and you can pull a 60". Sharpening them? Ya gotta hand file those bad boys with a 1.25 round file, its the only way. The guys that race Hot Trimmers will even square grind with 1.5 triangluar pattern filing, but they dull alot faster, but they are running jet fuel and alcohol at 16:1.......
What kind of hedge?