You can use the mag well adaptor for Glock mags. We have not heard much from folks running aftermarket Glock mags. They might work, but may not. If you try these out, let us know what you find!
The weight is a bit deceiving - there is more heft than you'd expect. This has worked well for off-hand shooting, as the rifle doesn't move much when firing!
Unfortunately, the stock is not being offered as a separate item as of yet (we have not heard if Ruger plans to offer any of the newer, upgraded items aftermarket).
We certainly hope not, but who knows with the feds...
KGL