You may have to try a few different weights of oil. I use 5-10 fork oil, belray, with seal swell (to keep the seals from leaking), and I have had to try a few different weights because the thick oil makes the forks stone hard, and the thin stuff makes them like mush. Depends upon you body weight and the tank size too. Gallons weigh a bit. Even matters if the tank is full or not to an extent....10 or 15 might be the right weight for the average Joe....you will get it comfortable if you experiment a bit.... :wink:
Since servicing my forks and fitting progressive springs and covenant damper kits I have used SAE20 fork oil. The covenant kit makes damping firmer, mainly at the extremes of travel. It also has an apparent effect of stiffening the forks slightly, due to a potentially reduced travel before bottoming.
Since I only weigh 145lbs wet through, I would prefer a softer and more compliant ride. Norbsa's modification to increase the operating travel sounds like a good plan, albeit with theoretical risks to the bearing loads.
I will be experimenting with different oil weights and suspect that SAE 15 or 10 might suit me better. The lighter oils should give a softer ride.