[racket] making flvector with C API?

I've got a little numerical routine in C that I'm calling from Racket;
I started out with passing in normal vectors, but then I dug through
the Racket source and found the macros necessary to handle flvectors,
and switched to that. Seemed to speed things up. I'd like to finish
the conversion, and return an flvector from my function, but there
doesn't seem to be a "scheme_make_flvector", like
"scheme_make_vector". Am I missing it? Does it have a different name?
Can I kludge my way to it? Could it be added/exported? Do I not
actually want to do this?

(I could of course modify in place an flvector provided by the caller,
but that isn't as satisfying.)

Thanks!

-- 
Jay Kominek