Don't forget that with the stock fitted the rear sight will be too close to your eye and will appear blurred (that's why the stock is so long to try and reduce the effect a little) and since recoil is such a key element to the firing cycle you will find that the pistol with stock fitted shoots very high. There was a front sight extension that fitted over the front sight and lifted it up a few mm. I have never seen one of these in the flesh.
In my HW45 days I did acquire a stock but quickly realised its limitations. By all means get one as part of a collection but don't get excited about the prospect....