Hmmm, since my main reason for light weight in a second is for travel...
In that case, I wonder if you are using miflex hoses and titanium 1st stages, because that would affect the travel weight far more than an ounce or two in the 2nd stage. Then again, bringing a 4 oz bottle of shampoo rather than an 8 oz would equal the difference between 3 or 4 of the 2nd stages, and maybe bringing a pair of cheap lightweight flip flops instead of nicer heavy ones might equal the difference between 10 of 15 2nd stages, and using a lightweight bag instead of a 10-12 lb suitcase might equal the difference between 100 2nd stages.
Point is, trying to actual save luggage weight by choosing a 2nd stage is probably not the most effective way to go about it. Neither from a luggage standpoint or regulator performance.
I routinely travel with 7ft, 5ft, 24", and 18" rubber hoses, 3 metal 2nd stages, 2 brass 1st stages, a metal backplate, canister light (which is the heaviest single item by far) wetsuit, jetfins (also heavy) 2 masks, reels, etc...and I never go over the 50lb weight restrictions for US airlines. The way I do it is by packing minimal clothes and toiletries (so far nobody has complained about my personal hygiene
) and using a lightweight-but-sturdy duffle with no wheels. Scuba gear outside of computers is pretty tough stuff. Probably the most delicate thing are the masks and they go in plastic boxes that have some rigidity. I carry the computer on the plane, and actually I shouldn't have mentioned the can light because I usually end up carrying that as well due to the battery restrictions in luggage. I don't really understand the rules and apparently neither do the airlines, because I frequently get a different story when I check in.
Sorry, I'm not trying to be contrarian....please go ahead and measure the weight of 2nd stages down to the gram. We don't have anything better to do during the pandemic!