Performance hit when using large font - why?

Today I decided to use a 42pt size for a GUIText font. I have 2/3 of the screen covered with this font size and it is scaled down. Previously I had a much smaller font size but that was not crisp enough on Retina displays. Hence, I choose a bigger font size. But now the performance has dropped to a 5 FPS, just by displaying the text. Any thoughts what I am doing wrong? Is it because of the scaling? The settings I have used are 42pt, custom font, dynamic, unchecked 2.x, normal style. Any help appreciated!