[plt-scheme] defaut slot values in Swindle

In Swindle, is there a way to use -defclass-auto-initargs- (or
something else) to make all class slots have a specific :initvalue
(e.g. #f)?  Alternatively, is there a way to have the maker generated
with :automaker use a specific value as the default value for optional
arguments that are not supplied?  Basically, I want this to return #f
instead of #<undefined>:

=> (defclass <foo> () x y z :auto #t)
=> (foo-z (make-foo 1 2))
#<undefined>

--dougorleans at gmail.com