bootstrapping on an older NetBSD without breaking existing installed pkgs?

[Carl Brewer <carl%bl.echidna.id.au@localhost>]

G'day,

I have an older NetBSD box that is due for upgrading, but it's not going 
to happen for a few months yet, and it's got pkgsrc pkgs installed on it 
that I would like to not break!
It's NetBSD 5.2.2 amd64

I understand that in order to continue to use pkgsrc on this older 
NetBSD it will need to be a bootstrapped pkgsrc rather than the vanilla 
pkgsrc that I have used in the past. Mainly, AFAICT, it's issues with 
newer pkgsrc not liking the older NetBSD make.  bmake seems to work, but 
there's some inconsistencies, and just making make be a symlink to bmake 
is a little scary :)

Best procedure to use?  Short of upgrading everything to 7.1 that is ... 
it's on the list!

Thank you,

Carl