Mike:
PRR tender lettering is 8" high, and the Microscale lettering is right on. The GHQ is probably too large. Depending which tender and era you are lettering however, the spacing is more of an issue. I actually used lettering from a diesel set to get closer to the correct spacing for the K4. The PRRT&HS modeling committee has been working with them to correct this problem and if you look at the artwork on the Microscale website, you will see a version with a variety of spacing. Unfortunately they only show HO images and they have not yet made this change on their N scale decals.