DocumentProperties Hatch page takes a long time to load in V7 with long list of hatches

I am noticing here that opening the Hatch page in DocumentProperties is very slow when I have a file open based on my own custom template - takes at least 5 seconds here to open. I have a long list of hatches in there, which is probably why. This did not happen in V6 with the same file and hatch list however.

This is probably related to this bugtrack item - I have added a comment.