Just to give an update...
This time I ended up filling the stock with lead BB's (.177 cal) instead of steel. Filled it near the top of the hole and then topped it off with a hot glue gun, let it harden, and put the butt plate back on. Hopefully that will keep everything in place but not be too difficult to remove if I ever need to access the stock bolt in the future.
Before weight: 6 pounds, 2.9 ounces.
After weight: 7 pounds, 6.6 ounces.
So lead BB size shot will add about approximately 1 pound, 3.3 ounces to a wood stocked pardner model.
Once I add the limbsaver slip on, the gun is about 7-3/4 pounds. Hopefully this will tame the turkey loads I intend to use this gun for.