Magento change amount of emails sended at once

Params:
Magento 1.6.0

Problem:
In Magento I need decrease of emails count wich will be send by cron at once.  Set this value to 8
and send emails every 5 minutes against default 15.

Solution:
Find and edit the following scriots by example.

Change count of emails in one action:
app/code/core/Mage/Adminhtml/controllers/Newsletter/QueueController.php
$countOfSubscritions = 8;
app/code/core/Mage/Newsletter/Model/Observer.php
$countOfSubscritions = 8

Change newsletter exec cron  time interval:
/app/code/core/Mage/Newsletter/etc/config.xml
<crontab><jobs><newsletter_send_all><schedule>
<cron_expr>*/5 * * * *</cron_expr>


PS:
This is bad solution, because  when you upgrade your store to the new version
those changes will be overwritten. If you not so lazy, create package for yourself ;)