mkext vs. tar for custom install

[Steve Kotsopoulos steve@ecf.toronto.edu]

I'm getting ready to load the CDROM onto my new PC (kfs filesystem), and
I can't use c:/plan9/386/bin/build because I only have 400Meg in my Plan9
partition. I want to load everything except /mips, /sparc and /68020.

If I did this with tar, I'd try:
% {cd /n/cdrom; tar c 386 sys lib acme rc adm} | {cd /n/kfs; tar xv}

If I did it with mkfs, I'd try:
% disk/mkfs -a -s /n/cdrom /tmp/myproto |disk/mkext -uv -d/n/kfs

Which of the above would be the preferred method, and why?
Would they both set the ownerships and modification times properly?

By the way, the manpage for mkext(8) says the '-u' option can only be used
when initializing a new fs(f) file system, but I find the following 
in /sys/lib/pcdist/src/build.c, where it un-packs the 4 floppies:

       sprint(buf, "vdexpand < /n/a/disk%d.vd | disk/mkext -uv -d/n/kfs", disk);

Here, it is using a kfs file system with the '-u' option, in contradiction
to the restriction in the manpage.
Is the manpage out of date, or is build.c breaking the rules somehow?