Hi alanediger!
In the past, I found that copying 3rd party hatch into the cad .pat file made it quite heavy to load the hatch previews...
Instead, create yourself a directory where you can save all your 3rd party hatch patterns...
Then, in your Support File Search Path (In Option...), add a path and browse the path where they're saved...
When launching the Hatch command, your hatch patterns will be in the "custom" type of patterns...
Hope this helps...
Mart