They are not significantly lighter. Material has been added to the lower case to make it less distortion prone when guys mount them on WIMPY mounts!
The cylinder bore is nickle plated, interestingly enough. YS is one of the few mfg's whose nickle plate doesn't fall off like brand O.
The cylinders never had a cooling issue, but the regs did down there underneath.

I'll have a load of these first part of April. Get your order in somewhere, the first ones are gone.