The trickiest aspect of these cheeses is getting the blue to grow inside what is normally, a very soft cheese. Maintaining some oxygen spaces inside the cheese to allow the blue to grow, without the cheese collapsing around the holes can be difficult. Herman's option of adding the PR into the center of the cheese during the make, which seems to be used by a number of people on the forum, will help, but you still need to get the piercing right and keep the piercing holes open. I found the drier curd helped a lot, but obviously too dry and its hard to get the soft gooey interior.
Keep experimenting, take lots of notes to help with fault finding, and you will get the balance right. Good luck