Parameters of GiST indexes

Hi hackers,

I found that some parameters of GiST implementation are builin in the code.
For example, following can be found in the backend/utils/adt/tsgistidx.c:

#define SIGLENINT 31 /* >121 => key will toast, so it will not
work
* !!! */

#define SIGLEN ( sizeof(int4) * SIGLENINT )
#define SIGLENBIT (SIGLEN * BITS_PER_BYTE)

I think that such parameters don't have optimal value for all the cases; and
it would be a great option to let user define such parameters for particular
index.
For example, following syntax can be used:

CREATE INDEX name ON table USING gist(column) WITH (SIGLENINT=63);

With best regards,
Korotkov Alexander.