ube--I have been using the 8 HST at a time method for a while and love how quickly and accurately the squaring up process is now with the Bloc-Loc ruler. While these are pricey, I think you really only need the 6 1/2 inch one or maybe the next larger size if you do a lot of larger HST as well. As I mentioned above, I like to have room for my hand to rest on the template and the little 2 1/2 one doesn't leave room for more than a finger.
Now I'd love to hear from anyone that has the flying geese Bloc-Loc's. I had to make a bunch of these for my last quilt and found the squaring up very tedious and had to stay very sharp to do it accurately.
I was reading a blog several weeks back that posted she didn't really recommend the rulers for the flying geese. Something about the method she used for making them and the valid point that you do have to buy the ruler for the specific size so multiple rulers would be required.