Need help to choose the right string

[red pepper]

My son 12 years old is breaking the strings more than once a week now, he is trained for about 10 hours for week, the main strings broke always in the same position in the center and between the third and the fifth cross string from top.
The strings are heavy notched already after 2 hours of play if I move the crosses they stick back in the notched position. Mains are moving a lot.
The racquet is a Wilson Kfactor Kpro Team FX and will stay the same for another year.
The strings actually used are Weisscannon Explosive in the mains @ 51 and the crosses are MSV Evo Hex @ 48. I change the crosses with Weisscannon Scorpion 1.22 (always @ 48) to try to have a bit more life but with this string in the crosses the ball stay on the racquet the shoot are much more shorter.
He has tested different setup full Explosive about same life time, full MSV Evo Hex at @ 49/47 he has the feeling that the shoot is unpredictable.
Evo Hex on mains and Explosive on crosses he don't like the feeling and he found also this setup unpredictable.
What I'm looking for ?
I'm looking for a strings with a life of about 20 hours before breaks or go dead so I can restring a racquet every 2 weeks and not 4-5 days like now, quite powerful and not expensive like rpm blast or alu power.
Could you please help me to get the right string ?

[DevilsChildXD]

Try getting 15 gauge strings and you say he breaks the strings at the same spot most of the time?? Go buy some string savers they work pretty well =)

[red pepper]

Should be read "always @ 48" don't know why I get the "cool" smiley

[mikeler]

Sounds like only poly or Kevlar mains will last long enough for him. What about purchasing a cheap dropweight stringing machine? Would he be interested in learning to string?

[finalfantasy7]

signum pro tornado 1.23, good durability, good comfort, ok power (could give you more) you do get loads of spin, comfort, feel, very good tension stability,

im using this on my k factor tour 90 as a full bed but im 23 and absoluely loving this, prefer this to my old set up_ luxlilon big banger crosses - wilson natural gut mains

as he's 12 try giving the signum pro tornado as just crosses, not sure about mains

[Carolina Racquet]

I would second the suggestion of the stringing machine... Would pay for itself in no time.

Would also help in experimenting in different strings and tension.

[kiteboard]

ash. kev./alu....

[pyrokid]

ash. kev./alu....

Pretty much.

I love a variation of this at a low tension.

[gunnd5000]

ash. kev./alu....

seconded or infact thirded.

also teach him how to string for him self!

[nvottennis]

Try the prince problend, or any kevlar hybrid. I'd be surprised if your kid breaks those in a week

[pyrokid]

Try the prince problend, or any kevlar hybrid. I'd be surprised if your kid breaks those in a week

Augh, not problend. That stuff is stiff even for Kevlar. :shock:
Not to mention ashaway gives you more of everything.

[Tennis_Crazed]

Try getting 15 gauge strings and you say he breaks the strings at the same spot most of the time?? Go buy some string savers they work pretty well =)

String savers are awesome! Worth the investment and trouble of putting them in.

[red pepper]

The broken strings is one problem, the other is that switching from Evo Hex to Scorpion with same tension he lost 3-4 meter in deep.
This is a fresh strung racquet after a training session.

http://i53.tinypic.com/2qlcnys.jpg

Kevlar is known for low power so I'm not sure it will help, I was thinking on a full poly that can give power.
I have read other threads and I get the opinion that SP Tornado or Polystar Energy will work for him.
Which one can run up to 15-20 hours with less tension drop and without goes dead ? 15-20 hours is too much for a poly?
Are string savers also helping to reduce strings movement?

I have a drop weigth stringing machine.
Thank you