Taking a flyer here.
I have a Q5SF Pro (with factory magwell). The 15+2 factory capacity is one of the only things I find disappointing about the gun, especially for the length of the factory 17 round magazines and what Walther gets for them.
The PDP full-size 18 round mags are barely longer than the factory magwell and appear to use the same follower design and magazine catch placement. They lock into the gun and work fine.
Is anybody aware of an aftermarket baseplate that makes the 18 round PDP mag index properly with the factory magwell? This seems like an obvious improvement over the Q5SF magazines.