optimizing import of large CSV file into partitioned table?

After careful research, I would to post the following problem I'm having
with the importing of a large (16Gb) CSV file. Here is brief synopsis:
- this is running on Postgres (PG) version: PostgreSQL 8.3.9 on
i486-pc-linux-gnu, compiled by GCC gcc-4.3.real (Ubuntu 4.3.2-1ubuntu11)
4.3.2
- it is running on a Ubuntu (small) server instance at Amazon Web Services
(AWS), with a 320Gb volume mounted for the PG data directory
- the database was created using the partition example in the documentation,
with an insert trigger and a function to direct which table where records
get inserted.
(see below for code on my table and trigger creation)

After some days of attempting to import the full 16Gb CSV file, I decided to
split the thing up, using the split utility in Linux. This seemed to improve
things; once I had split the CSV files into about 10Mb size files, I finally
got my first successful import of about 257,000 recs. However, this is going
to be a rather labor intensive process to import the full 16Gb file, if I
have to manually split it up, and import each smaller file separately.

So, I am wondering if there is any to optimize this process? I have been
using Postgres for several years, but have never had to partition or
optimize it for files of this size until now.
Any comments or suggestions would be most welcomed from this excellent
forum.

(I might add that I spend several weeks prior to this trying to get this to
work in MySQL, which I finally had to abandon.)

Sincerely,
Rick

Details of the code follow:

Here is the basic COPY command, which I run as the postgres user, to import
the CSV files:
<begin>
COPY allcalls FROM '/data/allcalls-csv/sub3ab' WITH CSV;

Here is what some sample data look like in the files:
3153371867,2008-02-04 16:11:00,1009,1,40
2125673062,2008-02-04 16:11:00,1009,1,41
5183562377,2008-02-04 16:11:00,1009,1,50
...

Here are the basic scripts that created the partition table and insert
trigger:
CREATE TABLE allcalls (
phonenum bigint,
callstarted timestamp without time zone,
status int,
attempts int,
duration int
);
CREATE TABLE allcalls_0 (
CHECK ( phonenum < 1000000000 )
) INHERITS (allcalls);
...(repeat this 9 more times, for 10 subpartition tables)

CREATE INDEX allcalls_0_phonenum ON allcalls_0 (phonenum);
..(repeat this 9 more times, for indexes on the 10 subpartition tables)
CREATE OR REPLACE FUNCTION allcalls_insert_trigger()
RETURNS TRIGGER AS $$
BEGIN
IF ( NEW.phonenum < 1000000000 ) THEN
INSERT INTO allcalls_0 VALUES (NEW.*);
ELSIF ( NEW.phonenum >= 1000000000 AND NEW.phonenum < 2000000000 ) THEN
INSERT INTO allcalls_1 VALUES (NEW.*);
...(again, repeat for rest of the parition tables)

CREATE TRIGGER insert_phonenum_trigger
BEFORE INSERT ON allcalls
FOR EACH ROW EXECUTE PROCEDURE allcalls_insert_trigger();

<end>