I found that when you have an iPhone with the dead lower row and iTunes saves your settings, it also saves the mods done in the touch.plist and the general.plist.
So when I upgraded that iPhone from 1.2 to 2.1 with the last Pwnage Tool on a Mac, it already had the touch sensitivity setting on place... It is a good way to update your iPhone with mods... because they does not disappear.
1- Backup with iTunes (on Sync)
2- Upgrade with iTunes to new SW version from Apple.
3- Use the latest Pwnage Tool to make a customized update file to jailbreak and/or unlock.
4- Connect to iTunes to recover all your things and hacked touch settings.