For reference:
Jostam HyGun - 7.1 oz.
Hawkins Repro Straight slots - 7.2 oz.
Hawkins Repro Trestle (hearts) - 5.7 oz.
Hawkins Original Trestle (hearts) - 5.5 0z.
Jostam No-Kick Coming - 3.7 oz.
Leather Kick Killer Lace-on (Large) 4.8 oz.
I have several Silver brand pads on hand but haven't weighed any of them yet.
Note that these are out-of-box weights and that much of it will be lost due to grinding down to fit.
IMO, anyone who worries over changing the balance significantly by adding a properly fitted pad needs a shrink, and shooting lessons, and might be a trapshooter, too.