The HSie hard coded fixes add a whole bunch of gameplay goodness, including some of the following (which are all selectable):
4GB patch
more torpedo failures
less bad weather
weapons officer moves to the bridge when surfacing
homoerotic interactions in the aft torpedo compartment
weather restrictions on reloads
blurry periscope views
restrictions on snorkelling
reduced visibility warnings when running at high time compression
u-tankers
pack attacks (which are only really good for comedy value as the AI is sooo bad!)
It's a must have to be honest but also a real pain to install, which is why most GWX folks run OneAlex as he's done it all for you.
https://www.subsim.com/radioroom/dow...o=file&id=4717 (I think!) Read the instructions very carefully, they are a bit confusing because Stiebler worked with H.Sie and added a whole bunch of extra stuff.