[racket] scheme_make_vector gc macros

We are experiencing some small memory leaks in Fluxus, and I am 
wondering if the garbage collector registration of the following code is 
right. It should return an array of float values as a scheme vector.
I read the part on memory allocation in Inside: Racket C API, but I'm 
not sure how it should be done properly.

Scheme_Object *FloatsToScheme(float *src, unsigned int size)
{
     Scheme_Object *ret=NULL;
     Scheme_Object *tmp=NULL;
     MZ_GC_DECL_REG(2);
     MZ_GC_VAR_IN_REG(0, ret);
     MZ_GC_VAR_IN_REG(1, tmp);
     MZ_GC_REG();
     ret = scheme_make_vector(size, scheme_void);
     for (unsigned int n=0; n<size; n++)
     {
         tmp=scheme_make_double(src[n]);
         SCHEME_VEC_ELS(ret)[n]=tmp;
     }
     MZ_GC_UNREG();
     return ret;
}

Any help would be greatly appreciated.

Best,
Gabor