..... in response to kid kc's inquiry....
I used to hunt for notes that were over-sized -- particularly 1937 and 1954 series -- and still take a small plastic ruler with me to shows. Occassionally I find an UNC note with huge borders -- as much as 1/4 longer than the dimensions listed in Charlton, but these notes often have bad centering. Call me crazy, but I personally like these notes.
I've NEVER done this, but if I trimmed an oversize note down to 6 inches long ( standard issue size ) it is technically a trimmed note, but still has proper dimensions, and consequently shouldn't have any decrease in value ( in theory ).
I've also found 1937 notes with huge borders that are 1/4 inch under size..... these notes I assume shrank when the cotton was wet, either in the printing process -- or by repeated washings over the years by various owners. Some short notes can have counting crease ghosts and other signs of being mucked with, and these I avoid.
Notes that have whisper thin borders have likely undergone repeated trimmings over the years. I avoid these a well because I don't like the look. Others however, don't mind, especially if it's a tough note.
As for the premium or discount that should be applied to an "original untrimmed" or "trimmed" note, well that depends on you -- and I don't believe there is a right or wrong answer. Buy what you like and pay what you can afford. If your only concerned about future resale value, then you'll have to be more selective.
Hope this helps.