PBXT tables very large on disk

PBXT tables seem to be extremely large in comparison to other engines on disk. Even outputting to a .CSV file still produce a filesize that is less than half of PBXT:

mysql> SHOW CREATE TABLE Logger\G
*************************** 1. row ***************************
       Table: Logger
Create Table: CREATE TABLE `Logger` (
  `timestampOccurred` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `dateOccurred` date NOT NULL,
  `session` char(32) DEFAULT NULL,
  `host` varchar(255) DEFAULT NULL,
  `sslMode` enum('enabled','disabled') DEFAULT 'enabled',
  `requestURI` varchar(255) DEFAULT NULL,
  `referer` varchar(255) DEFAULT NULL,
  `userAgent` varchar(255) DEFAULT NULL,
  `remoteHost` int(10) unsigned NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

mysql> ALTER TABLE Logger ENGINE='PBXT';
Query OK, 945463 rows affected (1 min 21.74 sec)
Records: 945463 Duplicates: 0 Warnings: 0

mysql> SELECT DATA_LENGTH / 1024 / 1024 AS Data, INDEX_LENGTH / 1024 / 1024 AS Indexes FROM information_schema.TABLES WHERE TABLE_SCHEMA='test' AND TABLE_NAME='Logger';
+------------+------------+
| Data | Indexes |
+------------+------------+
| 0.90166473 | 0.00390625 |
+------------+------------+
1 row in set (0.00 sec)

office101-221:test root# ls -lh
total 1195560
-rw-rw---- 1 _mysql staff 3.8M Apr 28 11:13 Logger-1.xtr
-rw-rw---- 1 _mysql staff 8.7K Apr 28 11:12 Logger.frm
-rw-rw---- 1 _mysql staff 580M Apr 28 11:13 Logger.xtd
-rw-rw---- 1 _mysql staff 4.0K Apr 28 11:12 Logger.xti
-rw-rw---- 1 _mysql staff 65B Apr 28 11:01 db.opt

mysql> ALTER TABLE Logger ENGINE='Archive';
Query OK, 945463 rows affected (13.85 sec)
Records: 945463 Duplicates: 0 Warnings: 0

mysql> SELECT DATA_LENGTH / 1024 / 1024 AS Data, INDEX_LENGTH / 1024 / 1024 AS Indexes FROM information_schema.TABLES WHERE TABLE_SCHEMA='test' AND TABLE_NAME='Logger';
+-------------+------------+
| Data | Indexes |
+-------------+------------+
| 27.35079288 | 0.00000000 |
+-------------+------------+
1 row in set (0.00 sec)

office101-221:test root# ls -lh
total 56048
-rw-rw---- 1 _mysql staff 27M Apr 28 11:08 Logger.ARZ
-rw-rw---- 1 _mysql staff 8.7K Apr 28 11:07 Logger.frm
-rw-rw---- 1 _mysql staff 65B Apr 28 11:01 db.opt

mysql> ALTER TABLE Logger ENGINE='MyISAM';
Query OK, 945463 rows affected (8.29 sec)
Records: 945463 Duplicates: 0 Warnings: 0

mysql> SELECT DATA_LENGTH / 1024 / 1024 AS Data, INDEX_LENGTH / 1024 / 1024 AS Indexes FROM information_schema.TABLES WHERE TABLE_SCHEMA='test' AND TABLE_NAME='Logger';
+--------------+------------+
| Data | Indexes |
+--------------+------------+
| 186.35408020 | 0.00097656 |
+--------------+------------+
1 row in set (0.01 sec)

office101-221:test root# ls -lh
total 381696
-rw-rw---- 1 _mysql staff 186M Apr 28 11:14 Logger.MYD
-rw-rw---- 1 _mysql staff 1.0K Apr 28 11:14 Logger.MYI
-rw-rw---- 1 _mysql staff 8.7K Apr 28 11:14 Logger.frm
-rw-rw---- 1 _mysql staff 65B Apr 28 11:01 db.opt

mysql> ALTER TABLE Logger ENGINE='InnoDB';
Query OK, 945463 rows affected (48.27 sec)
Records: 945463 Duplicates: 0 Warnings: 0

mysql> SELECT DATA_LENGTH / 1024 / 1024 AS Data, INDEX_LENGTH / 1024 / 1024 AS Indexes FROM information_schema.TABLES WHERE TABLE_SCHEMA='test' AND TABLE_NAME='Logger';
+--------------+------------+
| Data | Indexes |
+--------------+------------+
| 221.75000000 | 0.00000000 |
+--------------+------------+
1 row in set (0.00 sec)

office101-221:test root# ls -lh
total 475168
-rw-rw---- 1 _mysql staff 8.7K Apr 28 11:16 Logger.frm
-rw-rw---- 1 _mysql staff 232M Apr 28 11:17 Logger.ibd
-rw-rw---- 1 _mysql staff 65B Apr 28 11:01 db.opt

mysql> SELECT * FROM Logger INTO OUTFILE '/tmp/logger.csv';
Query OK, 945463 rows affected (8.04 sec)

office101-221:tmp root# ls -lh logger.csv
-rw-rw-rw- 1 _mysql wheel 215M Apr 28 11:20 logger.csv
office101-221:tmp root#

I wasn't sure if this was by design, but it seems like it could cost a lot of disk I/O? I was talking to a colleague (and fellow PBXT enthusiast) and he seems to think it may be an issue with PBXT not packing keys?