Modifying FreeBSD base?

[Ivan Fetch]

Hello,
   I'd like to modify the FreeBSD "base" (e.g. make changes to
configuration files) - is there a way to do this without make world and
creating my own distribution (the changes are simple enough I'd like to
be able to role them into a modified base for now).

   It seemd like I could do the following:
   1. cat base.?? > /tmp/filename.tar.gz
   2. cd /tmp; mkdir base; tar -C base -xpzf ../base.tar.gz
   3. Edit which ever files, and recreate a new base.tar.gz
4. use split(1) to split the tar.gz file up again
5. Recreate the CHECKSUM.MD5 file with lines for each base.?? file of the
form:
MD5 (base.aa) = md5_of_file

   Unfortunately the install complains about not being able to read the
base distributions (doing an FTP install).  What am I missing?  Somewhere
there's something else which appears to be telling the install it should
expect a certain number of split base.?? files (I end up with a larger
number of these, and can not seem to get split to let me create the same
number as originally existed in).

Thanks,
Ivan Fetch.