The string trimmer has to be pretty much on the same slope as the tow vehicle. My slopes are about 30 degrees worst case. I measured them because my tow vehicle engine specs are 30 degree max tilt to keep the oil (at normal levels) pumping. The string trimmer covers only about 18". Obviously the sickle a lot more......my experience was some times it covers too much.....like I had thought about cutting it in half so that it could only cut about 4' at a time....but that was more fantasy than reality considering what it'd take......but in reality it would have been much more workable around obstructions......so based upon that, my thoughts would be to look for the shortest, not the longest and the shortest would have fewer parts to maintain.