[Q] Update Cm7.2 to Cm9 !! Is Kernel Update Needed ??

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http://forum.xda-developers.com – Im having a DEFY mb525 . Red Lense (Camera Pics Take > 1mb size) I recently updated from Cm7.2 to Cm9 (cm9-nightly-121116) ,, But I just flashed the ROM without any Extra kernel Flash or battery Fix Now i feels my phone is discharging fast ,, So planned to flash battery fix as i missed it. r8 now my phone shows kernel as .... got kernel-gb-234-451-134-signed.zip from http://defy.wdscript.fr/kernel/ Before that my Questions are should i update the KERNEL .. its some threads its shown Kernal Update is necessary ... Can i go back to cm7.2 by just wipe and (HowTos)