I'm still kind of new on the forum but I know that the 10-round mag capacity of the HP carbines is a constant source of irritation. So here's an idea and if this has already been beat to death in another thread I'm sorry a thousand times and will never speak of it again. Cutting to the chase, why couldn't you take two HP factory mags (45, 40, or 9), cut the top off one and the bottom off the other, fabricate a longer spring (or repurpose one from a different stick mag), weld the two halves together and grind it smooth? Voila - a 20 round stick mag with properly-shaped feed-lips. Why not?