Looking through my own set right now, I think you could lose a few pounds by:
- Doing without the little windshield, pilot fairing, and cowling. It all appears to be cosmetic - near as I can tell, all of it is non-structural. Definitely check me on that, though.
- The plans call out "wheelbarrow tires" and, I assume, wheels. Very heavy. Go to Aircraft Spruce and get real ultralight wheels and tires. You'll pay more for them, but probably lose 2-3 pounds each, or more.
Note that all of the things I mentioned are at the front of the plane, however. You could remove them only to the degree that the center of gravity remains within the specified limits with you aboard and using the engine you choose. Your engine choice will affect the weight the most, but again, you have to make sure the airplane balances at the right spot, no matter what engine you choose. Your choices, therefore, are a bit limited.
I wouldn't even remotely recommend altering any of the structure of the airplane to reduce weight, unless you happen to have a qualified structural engineer (who knows airplanes) handy to check the consequences of your changes. There's just too many things that can go wrong, and most of them can hurt you pretty badly.
And really, there isn't much you can "add" to an ultralight in the end, so while I don't know what you had in mind, keep your desire to put more things onto the airplane to a bare minimum. Burt Rutan is quoted as saying, about parts to be put on an airplane: "Throw it up in the air. If it comes down, it's too heavy to be on the plane." He was only half-kidding. Anything you add will probably reduce climb performance and increase your sink rate if the engine should fail. Neither effect is something that you want.