I have the follow scenario :
Apache apache2.0.49 loadbalance amongst 2 tomcat instances (tomcat version is 
4.1.29).
This is configuration about loadbalance :
. httpd.conf :
Listen 80
ServerName 10.90.15.234:80
LoadModule jk2_module modules/mod_jk2.so

---------------------------------

2. workers2.properties file
[logger]
level=DEBUG

# Alternate file logger
[logger.file:0]
level=DEBUG
file=c:/Program Files/Apache Group/Apache2/logs/jk2.log


[shm]
file=${serverRoot}/logs/shm.file
size=1048576

[workerEnv:]
info=Global server options
timing=1
debug=0
# Default Native Logger (apache2 or win32 ) 
# can be overriden to a file logger, useful 
# when tracing win32 related issues
logger=logger.file:0

# define the worker
[ajp13:localhost:8010]
channel=channel.socket:localhost:8010

# define the worker
[ajp13:localhost:8011]
channel=channel.socket:localhost:8011


[lb:lb]
info=Default load balancer.
debug=1

[channel.socket:localhost:8010]
info=Ajp13 forwarding over socket
debug=1
tomcatId=TC1
lb_factor=1
group=lb

[channel.socket:localhost:8011]
info=A second tomcat instance. 
debug=1
tomcatId=TC2
lb_factor=1
group=lb

[status:]
info=Status worker, displays runtime informations

[uri:/jkstatus/*]
info=Display status information and checks the config file for changes.
group=status:

# Uri mapping for eMatrix
[uri:/ematrix/*]

# Uri mapping for default Tomcat Example
[uri:/examples/*]
---------------------------


With this configuration, if I try to upload/download file 
(http://xx.xx.xx.xx:9080 Apache Port) , usualy the transfer rate is about 
240Kbs, instead if I try with the same operation directy to tomcat port (same 
operation,same file) the transfer rate is about 5.1 Mbs. I try to put in place 
old "mod_jk2-2.0.43.dll" and modify apache httpd.conf file with the new 
directive "LoadModule jk2_module modules/mod_jk2-2.0.43.dll", now I have 
accetable value in termo of upload/download (about 1.6 Mbs still slow but 
accetable value).