I use my 45 degree line on my ruler to line up on the seam of my HSTs when I need to trim them down - yes, I trim all 4 sides the same amount and by using the 45 degree line, it keeps the HSTs in the proper proportion. I do the sides where the 45 degree line is on the seam line first, then do the other sides because I can then use the already cut edges to line up on the lines of the ruler.
I have never had to recut a quilt either, but I do like to make my HSTs a little larger so I can trim them down to perfection! Good luck on this project. I want to make a labyrinth quilt too - they look so cool!