just do it.
I did a few days ago,
I have 3 harnesses, 2 in use on a rotational basis and one as a dry spare to loan out or other,
all have them little finger hole line knives, all were 3-5 years old but looked like new, no rust.
they would not cut my kite line at all, even under tension-ping tight!
the knives just frayed the surface, and my power Q lines that I use, the knives would not even fray the surface.
and my test line is the north standard stuff!
this horrified me, because I am one of the very few who has been in a major kitemare situation years ago when I got lofted on the sea wall with compound leg fracture and kite powered up trying to hoick me back up for another lofting between the houses, my buddy tried to cut all my lines which i remember him screaming back at me that they would not cut, and believe me they were under great tension.
I threw all the knives straight in the bin and ordered a jack knife, parachute emergency line and strap cutter, similar to the finger hole harness line cutter but with a easy grasp handle and proven CE standard cutting power, when tested it was such a relief when the blades sliced through mutipel strands with a light 2 finger stroke.
delivered next day and fits in the harness pocket like the old useless ones.
twice the price but what the hell.