The 18-round magazine used in the PDP Compact Pro is NOT extensible at this time.
That particular magazine comes with a built-in overtravel stop that is part of the basepad. If you remove the basepad, you remove the overtravel stop. Without that stop, the magazine will try to pass up through the slide when the slide is locked back.
The only thing preventing this from happening is the ejector -- and with a good shove you can break the tip of the ejector off, killing the gun.
We've spoken with a couple of shooters that have done that already, so beware!
NOTE: Full-size magwell does not work on VP9 with large grips installed.
What size is your PDP Backstrap?
Our PDP full-size backstrap mimics the Walther "medium" backstrap.
Do Your Walther PDP Parts fit the PDP Pro?
The PDP Pro (as we understand it) is a PDP with cool accessories.
Assuming yours is a full-size gun (18-round flush-fit mags). Everything we make for the PDP full-size should fit. That said, I'd advise you to buy the whole set at once if you intend to use our magwell.
The basepads and the backstrap work as stand-alone products, but the hardware to attach the magwell is built into the backstrap (the magwell won't attach without it). Also, once you attach the magwell, you'll need extended basepads of some sort to get the mags to lock in properly.
PDP parts won’t fit my PDP magazine!
Sounds like you have a PDP-C (Compact) with the 15-round mags. If you do, you want parts for the PPQ/PDP-C magazine. Walther - PPQ - Page 1 - Taylorfreelance (taylorfreelancestore.com)
The PDP (full size) magazines are narrower, similar to a CZ or a Canik.
Looking at your order, you ordered a +0 for the Canik. That won't work on a PDP-C, and it won't work on the PDP full-size either -- the shoulders have to be milled off slightly to let the magazine go far enough up into the frame to lock in. (It's a common misconception that Canik mags and mag parts work on the PDP -- they ALMOST do, but not quite.)
I have a Walther PDP Pro SD Compact, and I would like to know if the Full Size 18 round PDP mag with your baseplate will fit like the factory 18 round mag that also has an aluminum baseplate.
Currently, the mags you have are NOT extendable. The basepads we make will fit that tube, but that's only half the story. The "skirt" that covers the exposed part of the long mag tube in the PDP Compact also acts as an overtravel stop. If you remove that overtravel stop, the mag can (and will) strike the ejector when you're reloading with the slide locked back -- potentially damaging the ejector.
The risk of overpenetration damage is more or less serious in different guns -- but in yours, it's quite serious. (We know shooters have broken their ejectors completely off.)
Until we can produce a system for stopping overpenetration, we recommend leaving those 18-rounders as-is.
Will the PPQ +6 mag extension work on the PDP Pro