Override the number of DNS lookups

Is there a way to override the number of DNS lookups?  I know the SPF=20
standard says 10 but SpamAssassin and other software does a few more=20
lookups.  There are so many mail admins out there that don't understand=20
how to properly setup SPF on subdomains for sending from third parties=20
on their behalf to keep DNS lookups at 10 or less.

It would be helpful to allow for 15 to 20 lookups.

--=20
David Jones