buildign patched installations?

[carl@bl.echidna.id.au]

I had a look through the doco and FAQ, but didn't find anything 
about this (but, I may have missed it ...)

I want to build 4 boxes, all with 2.8 + current
patches, so I figure I'd build one, and then make 
base28.tgz etc, and use them to install the other boxes.

A quick look through the makefile in /usr/src didn't
show me any shortcuts to doing this, nor did anything I could
find on www.openbsd.org or a troll through this lists's
archives.  I can always just use tar -tf and then feed that
back into tar, but has that already been done and scripted somewhere?

Any clues?  Pointers to doco?

thanks

Carl