I just got my two 4D 100's yesteryday.
First off, it is a badass looking racket.
Second, i can tell already I like the weight and balance, very PS85'ish.
Third, lengthwise the head size is the same as my 4D 200, it's just a little more narrow, shouldn't be a problem.
Got a match tonight, not sure if I'll chance using it for USTA league but maybe, kind of excited. This might be the answer to a regular 4D 200 but with a more open string pattern.