I haven't been fooling around with these numbers for a few months, that figure of 0.440" is wrong, the thicker pad makes the caliper stick out further. I have the stack number somewhere... The Wilwood kit uses a hat that's about 0.600 so if we leave the inside face location alone the hat goes to around 0.160". It should be easy to make the hat light weight but it will certainly need threaded inserts to keep the rotor bolts from pulling out. I would love to design one of those floating rotor setups that use a locking ring instead of bolts but the machining might be difficult and it might require the interior of the rotor to be more precisely machined than the cheapo rotors are. I've been thinking about this since last summer but the lack of 6ul wheels and personal time has kept this a mental exercise.