In another thread, this was mentioned.

Quote from: anwar on February 05, 2010, 05:43:05 PM
4) "Chinese weighted" tails, for better tail stability/performance.

A basic explanation is here : http://www.rcheliwiki.com/Chinese_weights

A detailed explanation of what this is and how this helps is found here : http://www.helifreak.com/showthread.php?t=78453

This "mod" causes a significant enough improvement in tail performance, that all recent models of small helis from well known brands have all started incorporating this into their tail rotor design.  It is said that this mod makes the tails of small helis perform with the kind of tail stability that is usually seen in their bigger cousins.

Does the PRO grips need this mod or are they good? If yes, we can use the pro grips on the V2 instead of this mod.

I did a small experiment on the V2 grips which went all wrong . I used a lock nut and bigger screw (to add some weight) to hold the tail blades. During a test flight, I don't know what happened and one of the tail grips came off!

the pro and the V3 already the chinese weights installed.. infact more than a 450.... for a 250 this was a serious issue and align released the 250Se version with the chinese weights which solved this problem to a certain extent (my own personal experience).
your experiment worked for me on one of my helis SJM 250pro (which infact already had chinese weight) but i increased it with by placing a ball link on either side of each rotor blade.