Care to share this test with us? A link? A book? An article?
The laws of physics don't quite agree. The results of that test would also say that you can produce just as much pace with a 15 inch racket as you can with a 27 inch racket, or a ping pong paddle for that matter. I would be very interested in reading more about this little test.
To the OP, please check this thread
http://tt.tennis-warehouse.com/showthread.php?t=168561&highlight=
Here was my response to the original question:
The ball comes off the stringbed of a 28 inch racket the exact same way as it would an indentical racket with an inch or even two inches cut off. There is no change in "control". The only change is in your head, your own perception. It is due to the fact that your own inaccuracy is exposed. I would go so far as to say you have more control with an extended length racket. Becuase of the increased reach, there is the possibility to hit shots that are not possible with a shorter frame. That is not the whole story though.
The increase in length and the increase in leverage makes it easier to miss. If you miss a little bit with a 26 inch racket, you're going to miss a lot with a 28 inch racket. Timing is much easier with a shorter racket, as is the margin for error. Because of the smaller margin for error, It is most likely easier to have a bad day with an extended length rackets. You can miss by a significantly larger distance than you might otherwise, causing you to feel a like the court is shrinking around you, which I think can easily to lead to a feeling of less precision and even a loss of confidence.
As far as length goes in other aspects, it is extremely important. The increase in pace on serves without a comparable increase in effort can be significant, same with groundstrokes. The increase in leverage has a larger impact than an increases in weight when it comes to a racket swing. The same speed swing relative to your wrist/arm gives a higher speed at the tip of the racket. A shortened racket can put you at a tremendous disadvantage once you get to a certain level in this game. Why 27 inches works out to be the magic number, I have no idea...