another DEFSTRUCT clarification

[sandra%defun@cs.utah.edu (Sandra J Loosemore)]

Does using the :CONSTRUCTOR option to DEFSTRUCT to define a BOA
constructor disable it from making the default keyword constructor?  I
have always assumed that you had to explicitly say (:CONSTRUCTOR NIL)
if you did not want a keyword constructor, but it's been pointed out
to me by one of the other people here that CLtL doesn't actually say
that, and that the behavior of the various Lisps we have here differs
on this.  

Also, can (:CONSTRUCTOR <name>) appear multiple times to get multiple
copies of the keyword constructor?

-Sandra
-------