[CentOS] update from 4.8 to 5.4?

I have searched the list, and don't see this covered or didn't search for the 
right words.

I'm running CentOS 4.8 and have some DVD's for 5.4. I have a lot of customized 
and additional software installed and would like to avoid starting over with 
a scratch install. After the upgrade from the DVD I would do a yum upgrade to 
5.5. 

Is this a workable (and safe) thing to do? What should I look out for? 

I plan to build a clone of the boot disk in case there is a problem so I can 
swap it back in to the hba1 position (as soon as I find a way to make a clone 
of a disk with LVM ).

Here is some info on the system:

[root at hat /]# cat /etc/redhat-release
CentOS release 4.8 (Final)
[root at hat  /]# uname -a
Linux hat.rbt.net 2.6.9-89.0.25.ELsmp #1 SMP Thu May 6 12:28:03 EDT 2010 i686 
athlon i386 GNU/Linux[root at hat .spamassassin]# df -h
Filesystem                           Size      Used  Avail   Use%   Mounted on
/dev/mapper/VG00-LV00     2.0G     695M   1.2G   37%   /
/dev/hda1                            494M    25M    444M     6%   /boot
none                                    1013M  0       1013M     0%   /dev/shm
/dev/mapper/VG00-LV04     9.9G     5.4G    4.0G   58%    /home
/dev/mapper/VG00-LV05     1008M  34M    924M    4%    /opt
/dev/mapper/VG00-LV03     4.0G     41M     3.7G     2%    /tmp
/dev/mapper/VG00-LV01     7.9G     4.2G    3.4G   56%   /usr
/dev/mapper/VG00-LV02     4.0G     929M   2.9G   25%   /var

Thanks in advance for any help with this....

Bob