I am currently doing a test upgrade of a freshly installed 11i vision instance with database 188.8.131.52 to database version 184.108.40.206. Till now I have achieved the following:
Install Oracle Enterprise Linux 5
Install pre-requisite patches for 220.127.116.11 on OEL5
Install E-Business Suite 18.104.22.168 Vision instance
Apply pre-requisite patch ATG_PF.H RUP6
Install 11g software
Executed catupgrd.sql successfully
Recompilation of invalids is in progress now.
I'll update this post with more details about this activity.