Local Beach: Casuarina Beach Rapic Creek Lee Point Buffallo Creek
Favorite Beaches: Old Woman Rock, Darwin Oka Point, Sanuar, Bali Phan Rang, Vietnam Cemetary's, Mui Ne, Vietnam Point Moore, Hells Gates, Geraldton, Western Australia Rapid Creek, Darwin, Australia Lee Point, Darwin, Australia (my local spot) Nugas/Lakey Peak, Sumbawa Marion Bay, Tasmania Long Beach, Robe, South Australia
Gear: Ozone Edge 19m North Evo 14m North Rebel 12m North Rebel 9m North Rebel 7m North Nugget 5'5" Surfboard North WAM 6'2" Surfboard North Whip 5'6" surfboard North SkyPro 138cm TT Underground FLX 144 TT
... line sponge is very real thing and I remember another little experiment I did which showed up the very thing you mention, heavier steering.
I went to a local yacht shop and bought the best line they had to replace the single line that goes from the depower strap to the front Y point. It turned out to be really spongy and each dive of the kite, the kite would distort and the bar got heavy. If I dived the kite slower and let it creep up and down it wasn't as bad but load it up, it got worse. What I concluded was the kite angle of attack changed and the kites back lines were too short during the flexing, choking the kite. If you choke the kite, steering gets worse and you notice this as heavier bar pressure. Without the line flex the AOA stayed the same and therefore wouldn't choke and steering is normal.
There must be some stuff or treatment on lines that must wear off after time. I noticed that after a few months the lines would get little fibers hanging out, sort of looks like it gets furry. So I figure that if the outside parts of the line wear, maybe the inside fibres are wearing down too making the line thinner by enough to cause the flex we feel. Over 20 to 30m of kite lines, this is enough for us to feel it as spongy lines.
I'm overhauling the SS bar with thin lines. Obviously the CSS will not be used due to line length differences but I like some of the SS bar components, very solid chicken loop base compared to LF. I will then fly the REV and see how it goes. Of course I will loose performance but I purchased the REV for its stability in gusty garbage NY great lake winds not kite loops. Will post my experience.