Have a look at this extended USP40C Magazine with a Horse Foot Floorplate

[Hk-USPC-40]

This is in a thread @ HkPro about Suppressor sights for the USP Compact..
gumby510 cut a 10 round mag + a 12 round & mig welded them together & used a longer spring from a USP 40 high cap magazine
Says it holds 15/16 Rounds
He looks to be a car guru, I'm going to PM Him & ask to Join Here..
Looks Very Tactical, I also note He says something about 40/10mm too??

https://www.hkpro.com/threads/suppressor-sights-for-usp-compact.530450/#post-3812125

 

[AGG]

Interesting--- but really?

Tony

 

[MMissile]

Lots of cool stuff.....but isn't the compact aspect of it gone?

 

[Hk-USPC-40]

You are correct Sir..
Stuff hanging out everywhere..

 

[Gumby510]

Lots of cool stuff.....but isn't the compact aspect of it gone?

Well, I dont carry it like that. I have a different setup for that. Standard height sights and 12rd mags with both the flat and finger baseplate.