Unable to change bootloader topic

Hello expert,

i try to go from stock asus JB to KitKat 4.4.4-CROMBi-kk-R1-Oct 1
i have tried to follow up the provided instruction http://forum.xda-developers.com/show....php?t=2773812 #4
- root the tablet (for titanium)
- i have unlock the bootloader and retrieved nvflash blob (so i should be able to unbrick if necessary)
- i have fastboot twrp_tf201t.blob --> OK
- adb push HairyBean_Bootloader_TWRP2.5.zip /sdcard --> OK
- flash this with TWRP --> OK
so far so good!
Now i reboot and i have the blue bar filled very fast and then it reboot but on android not on TWRP recovery -> ? --> I force the recovery mode to load by power and vol down + RCY
i tried adb reboot-bootloader but it makes the tablet reboot to android . if i restart with power and vol down i still have the USB icon so it seems that i can't upgrade the bootloader
Do i missed something or can i try something else? ( i already tried to wipe dalvik, cache, data, ( even system and they i had to restore my backup)
So i'm not bricked but cannot go forward :o
thanks for help
(and Sorry for my poor english )