I've found that the grab structure doesn't grab exactly the same structure, at least against mysql.  For example you have the following table "BillHistory" 
described as follows:
mysql> desc BillHistory;
+-----------+----------------------+------+-----+---------+----------------+
| Field     | Type                 | Null | Key | Default | Extra          |
+-----------+----------------------+------+-----+---------+----------------+
| HistoryID | int(10) unsigned     | NO   | PRI | NULL    | auto_increment |
| BillID    | smallint(5) unsigned | YES  |     | NULL    |                |
| DatePaid  | date                 | YES  |     | NULL    |                |
| TransID   | bigint(20) unsigned  | YES  |     | NULL    |                |
| VendorID  | smallint(5) unsigned | YES  |     | NULL    |                |
+-----------+----------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

You grab the structure of this table and create another table, "BillHistory2", using the grabbed structure and you get:

mysql> desc BillHistory2;
+-----------+-------------+------+-----+---------+-------+
| Field     | Type        | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| HistoryID | int(11)     | NO   | PRI |         |       |
| BillID    | smallint(6) | YES  |     | NULL    |       |
| DatePaid  | date        | YES  |     | NULL    |       |
| TransID   | bigint(20)  | YES  |     | NULL    |       |
| VendorID  | smallint(6) | YES  |     | NULL    |       |
+-----------+-------------+------+-----+---------+-------+
5 rows in set (0.01 sec)

While you can argue that the data size of the fields HistoryID, BillID, VendorID are the same (the unsigned is dropped, but the size is increased) this isn't 
true for TransID.  In BillHistory2 you are now limited to a max value of 2147483647 because it is signed whereas being unsigned in BillHistory you have 
upto 4294967295.  Also, the auto_increment is left out for HistoryID in BillHistory2.

The SQL to create BillHistory is as follows:

create table BillHistory (
  HistoryID     int unsigned auto_increment primary key,
  BillID        smallint unsigned,
  DatePaid      date,
  TransID       bigint unsigned,
  VendorID      smallint unsigned
);

and I'll attached the billhistory grab file that was used to create billhistory2.

Thanks.