Your method is correct but I do not understand why you need so little weight to balance. I guess it is possible to use a 39% balance factor it just reduces vibration in the horizontal direction (relative to cylinder axis, and increases vertical vibration. I do not know how free the rod is on the crank, in the video above its a roller bearing crank with a lot less friction than your setup. You may want to slowly add weight till it stops any place you put the crank then add small washers one at a time till it starts going down and it no longer stays where you put it and if it is more than a washer or two then you have a friction issue causing inaccurate results.