So (I think I'm on the right page
) putting your ghost back to 'what you would get today off the shelf if you bought an hp ghost' in the smaller 2 calibers, you found it a bit air wasteful/louder than necessary compared to your mods? I believe your results, I see the ghost as one of my favorite platforms and Brk bills it as a 'one system/size does all' - swap barrel sit at the bench and tune reg or hammer spring for 10 mins with ammo choice and off you go, but I think it probably leaves a bit of power off the top (bigger calibers) and probably a bit air wasteful on the smaller calibers. Lastly you found the lighter hammer you made - gave you a better fps adjustment range with your wheel then? Thanks again for the info!
My Ghost was a bit of a complicated path...
Mine is one of the first couple in the US. It started life as a 177 Carbine. It came with the skeletonized (lighter) hammer. At one point an AOA rep told me he suspected that this lighter hammer was intended for the sub12fpe guns in the UK. But I've since seen hammers from sub12fpe guns and they're not this one. I've seen 5 hammer variations, either personally or photos online or that people have sent me. My light one weighs 455grains, and my heavy one weighs 545grains. The heaviest I've seen or know about weighs 592grains. The earliest hammers had a threaded rod in the nose that allowed the hammer "throw" to be adjusted, ie the distance it traveled was controllable. As far as I can tell, the hammers in current production Ghosts in the US are the 545grain variety (solid sides, no cutouts), without the adjustable nose/throw length.
For most US guns, the 545grain is probably the most appropriate for the power levels most guys are wanting their Ghosts to shoot.
I personally REALLY like the 455grain hammer, but it's place to shine is mostly under 35 or so fpe. I feel the shot cycle is more crisp with the lighter hammer and conservative fpe output. I would not want the 455grain hammer if I was mostly running my Ghost in the 35+fpe range, as a .20 or I'm the 45+ fpe range as .22. Even to get to 35 fpe as a .20, my little hammer needs 38grains of weight added to it, which is how this discussion started. And the 38grains made the .22 go from a 40fpe gun to a 52foe gun.
I'm not sure how a "standard" 545grain hammer responds to adding weight to it, but based on what only 38grains does to my light hammer, more oomph could probably be had by only adding a relatively small percentage of weight. This would mostly be for someone pushing .30s, .25s, or heavy .22 slugs even.
There's also the question if efficiency. There's some overlap between the effects of adding hammer spring preload and adding hammer weight. Educated guess is that current production Ghosts could be customized to the owners desires and tolerances for cocking effort and shot cycle, via toying with hammer weights. Ie, reduce the cocking effort by adding more hammer weight, and keeping fpe output where the owner wants it. Yes, this is for the sickest and most afflicted tinkerers amongst us, but worth it, for those who care enough to experiment.
The lighter weight hammers biggest benefit, to me, is a snappier, more crisp shot cycle. Again, at the fpe output I'm after with a .20.
The hammer weight concept is simply another way to customize the Ghost to the owners wants, needs, and preferences.
. I really don't feel they get all that they pay for, for such a cool capable platform. Your shooting .20 slugs and pellets out of the same barrel right? Can I ask what your twist is on it?
Consistently off is one thing, but...how wide of a target is that? 2 1/2inch groups @ 100 ain't baaaad, that's a dead starling 6 out of 11 shots? Looks like my brother's 350 magnum .177 groups @ 40/50y. But I have never shot out to 100 yet myself. I say when those new Mrds are back in stock get a tin of each and retest, and of course... post results! 
Does your ghost refill the plenum pretty quick after each shot? I recall Tec had his reg cranked up and had to wait a few extra seconds for it to refill between shots.
