I will do a weight comparison once I pull the assembly apart (doing the dry-build right now), it is lighter than stock (just by feel) but the stock triple is actually not too bad weight wise, I was expecting it to be way heavier. The stock steerer is actually very light, and sans a titanium unit, is race ready weight wise IMO. The lower clamp is where I actually shaved some grams here, it isn't radically lighter, but my clamping surface is 1.8" long and mega stiff, when I pull the top clamp with the bike loaded on the front wheel, the tubes stay nice and parallel with the steerer, and the top clamp just slides back on.
The top clamp is lighter, but not by a huge margin either. I have made units from ZK-60 Magnesium, but diminishing returns was the order of the day with that material. No matter what the figures say about particular Magnesium alloys (PSI-tensile etc.) the nature of it requires that you got to meat it up, to the point where even 6061-T6 ends up beating it, because you can make much thinner wall/webs etc. Long story short, Magnesium is fantastic for wheels and covers, but for clamps is not so great IMO.
As to producing this stuff, I am overloaded as it is with what I produce normally, this is just one-off stuff for stress relief.