What is the source of the titanium brake caliper pistons? The banjos and bleeders are available in aluminum, which is lighter yet. Aluminum washers are also available, which with the aluminum hardware, may minimize galvanic corrosion. The nut on your front axle looks like aluminum. Is it? My K6 uses a heavy steel bolt that I've never liked. Titanium rotor mounting bolts are available. ProBolt and ProTi have nice stuff but it's expensive. You can get significantly cheaper bolts on ebay and AliExpress. I've replaced nearly all of the external bolts on my K6 with titanium, ex. for the clutch and generator covers. Gun drilled titanium caliper mounting bolts used to be available with weights that approached that of aluminum. The rear axle nut is available in titanium from ProBolt but it's not a locknut and is too expensive. Something similar is available on AliExpress for one fourth the price. Titan Classics has it as a locknut but but it's pricey. Lightech sells the bolts that attach the valve cover in aluminum with various colors. The bolts that attach things like the throttle cable guides and the brake reservoirs can be replaced with aluminum. I'm currently trying to replace the spacer for the fuel tank pivot with magnesium. A carbon fiber spacer would be lighter yet.