reason for default PGSTAT_ACTIVITY_SIZE

From my angle, it looks as if the default for PGSTAT_ACTIVITY_SIZE is
too small, or rather that it ought to be configurable at least, so
that longer current_query strings that are shown via
pg_stat_get_backend_activity() in the system view pg_stat_activity
aren't truncated.

The use case is to watch pg_stat_activity when troubleshooting a
busy/struggling live server which is building up a queue of long
running queries, to be able to see which of your SQL is most
problematic, and where it's coming from: We append a code reference as
a comment to all SQL that is sent by the ORM (we use a python web
application development framework, namely Django), in order to figure
out where it originates, which is otherwise tricky with SQL that is
generated by a translation layer - and this code reference is often
cut off because the string is limited.

Is there a good reason to set PGSTAT_ACTIVITY_SIZE at 256 and is my
only option to recompile the server? Is there a practical
limit/drawback to making the variable say 4 or 8 times the default?

I am referring to this post here:

http://archives.postgresql.org/pgsql-sql/2002-05/msg00087.php

and this one:

http://archives.postgresql.org/pgsql-novice/2004-02/msg00187.php

according to which recompiling would be the only option, but that was
a few years back so maybe it's a different story now.

Regards,

Frank