seeking a bigger ramdisk in wm6.1 rom

[k_blal]

hi guys i took Syed Ather Windows Mobile 6.1 Professional rom...i looks great, but the ramdisk is not sufficient for me so followed the steps of c-shekhar
the rom can be found
http://forum.xda-developers.com/showthread.php?t=372007

1. Extract NK.nba
> xda2nbftool -x NK.nbf NK.nba 0×20040304

2. Open NK.nba with a Hex Editor
3. Go To Address 0x00456250 (since this is a WM6.1)
4. modified as follows:
FF FF FF FF FF FF FF FF FF FF FF FF 00 00 00 04 --> 64 MB program, memory: RAMdisk= 64MB
4. Updated the Image Check Sum
> xda2nbftool -c -u NK.nba

5. Repack as NK.nbf
> xda2nbftool -x NK.nba NK.nbf 0×20040304

6. Put in the same directory as HimaUpgradeUt.exe or HimaUpgradeUt_NoID.exe

7. Flashed normally

but !!!!!!!!!!!!!!!!!!!!!!!!
i have a problem i keep getting the error that the check sum is incorrect

can any one tell me were is my mistake ? please any one ?
one more thing i didn't know how can i modify the nk.nba to change the registry for the right size of the ramdisk !!! so that when i will flash this rom i will get all these changes delete