VARCHAR w/Allocate vs. CHAR

Because I am, an MS SQL DBA that's had several DB2/400 questions on this
list, it was suggested to me that I read the red book "DB2 UDB for iSeries
Porting Guide: SQL Server to IBM eServer iSeries".  This has turned out to
be a great read for me.

On page 11 there is a section on character types that discusses the use of
CHAR over VARCHAR(50) or less.  I have a schema that does not follow this
because I built it before reading this doc.  Now, I'm curious about the
alter table statement and the ALLOCATE command.  Am I better off altering
the schema (40 tables) to use CHAR instead and go through the process of
porting information over, or can I get similar performance by changing the
allocation attribute.

I understand how ALLOCATE adjust my record/page level storage.  However, is
there some other significant cost to using VARCHAR (i.e. CPU).

Right now I am thinking I should alter my exsting tables using ALLOCATE to
keep things simple.

Thoughts?