Need the C2 experts to comment on your setup Bacho. A new jib may help but did a lot less than we thought at Nationals. Have a new main, but have yet to try it, supposedly they powered up the new sails and increased the range, I felt our 08' Performance Main had plenty of depth compared to the 13' sail but the newer sail can be trimmed flatter. If you're healing rather than accelerating in the puffs, this tends to be a worn out sail issue.

2nd hand information is the new C2 spreader range is 55-65mm, old range is 45-55mm. I would start at 50mm and a base diamond setting of 38 on the loos gauge.

The jib trim is also much more critical than the I20. The outer edge of the car should be just inboard of the 2nd post on the traveler, but again this varies based on traveler setup, breeze and sea state.

Also, need to sit way forward on the F18 in the light and especially lumpy. Helmsman at he forward beam, crew forward of that and even further forward (like bridle wires) if it gets lumpy. I think you can stay a little further aft on the C2, less stern to dig in but it's not a thin N20.

Finally, the i20 is faster in 0-5kts of breeze at the same crew weight. No way around it, more sail area, 2' more waterline and < 20lb platform weight difference makes for a faster boat. F18 Long boards have leveled the playing field in >5 kts of breeze, and when you need 420 lbs on the wire on the N20, 350lbs will keep the F18 nice and flat; plus the F18 hull shape is faster upwind in >12 kts of breeze, and we can carry the kite 10 degrees higher on a reach.