Hi,
I found the mod 5 to be better than I expected.
See me shooting it and the Heanel 28 @4:00mins and @6:18: https://youtu.be/qt2zfenq4QI
IMHO they both suffer from the same problem: The leather breech seals become compressed with use and the barrel starts to point up fractionally and your poi shifts up.
I fitted a PU breech seal to the Mod 5 which stopped that happening and once zeroed I found it very accurate. The grip is a bit basic but I'd be happy trying pistol HFT with it, shooting 40mm killzones out to 25yds. I bet it would get a few.
The 28 suffers from the same problem due to the way you cock it, basically putting upward force on the barrel, and I found the poi shifted up annoyingly after I thought I'd zeroed it. It would definitely benefit from a PU breech seal.
I found the Mod 5 is more powerful and accurate but the 28 has excellent balance so maybe you'd get good results from one due to the better ergonomics.
Both great pistols, be interested to hear how you get on.
Cheers,
Matt