Thanks for the advice, everyone. I ended up getting a new 34 Gen 3. It came with 2 17 round mags that were permanently blocked at 15 by the LGS.
Oh interesting. I guess I wasn't aware anyone was doing this. In fact, for many of the reasons above, I've been shooting a (Gen4) 19 for the same reason but would love a Gen4 17. Been thinking about a 34 myself, but for competition only.