It has not been difficult for me to get equal length lines as I follow the method outlined in the video. I have made up maybe 10 or 12 sets of lines for myself and other flying buddies and I have come up with a good system that works well for me.
1. I lay out my 60' line marker on the ground.
2. On the 1st line, I stretch the line (65# test) to 25 lbs and hold to get some initial stretch. Then I pull the line to 8 lbs and mark the line w/ a felt tip marker at the 60' mark. Then make up the double loop per the video at the mark point.
3. Then I repeat the same sequence for the second line.
My lines come out pretty much equal length, maybe within 1/8" +/-. I compensate at the hard point handle via the handle adjustment feature.
Ken, a bit more info on how I make up my lines to get equal length. I don't use a flying model to make up the lines. I make up the lines in my back yard.
I have an eye screw attached to a simple 2x4. The cinder block works as an anchor so I can pull (stretch) without movement.
1. I cut 2 lines maybe 6'-7' longer than the line length I want.
2. I make up a double loop on each line per the knot-tying video and attach to the eye screw with a zip tie.
3. I measure 60' away from the eye screw and mark the length point on the ground.
4. Then as previously stated, I start with one line and pull to 25 lbs and hold to get some initial stretch. (I use a digital fish scale)
5. Then I pull the line directly over the 60' marked point on the ground to 8 lbs and mark location with a felt pen.
6. Then I make up the second double loop per the knot tie video at the felt tip mark point on the line.
7. Then repeat the entire process for the 2nd line.
Lines come out even length.
BTW, the 25# stretch load and 8# length-marking load are somewhat arbitrary. For 65# Spectra, I wanted to stretch the line a bit less than 1/2 the line ultimate strength. The 8# length-marking load is a bit more than the flying load for a reasonably heavy model. Round numbers, a large stunter flying at say 60' and at a 5 sec lap time maybe pulls 10-12 lbs at the handle, or 5-6 lbs on each line in level flight.