Upgrade from 11i 11.5.10.2 to 12i 12.1.3 questions/comments

Hello   I have worked with applications since 1999 (10.7 nca), and did the 11.5.9 upgrade as well as the 11.5.10.2, so I have some idea of what to expect for most applications upgrades and patches.   I've also done DBA and development work since 1987.   I am in the process of preparing and doing our upgrade from 11.5.10.2 to 12.1.3.   I'm in the second test upgrade at the moment and was curious about others' experiences with some of the following:


1)   We are on a two-tier forms/web  - conc/db server setup.  The first test upgrade I did I tried to keep this configuration but it didn't go very well.   Nothing huge, but a lot of configuration modifications along the way to get the layout the way I wished and correct things that rapidwiz did (or didn't do).   I am trying this second test upgrade with apps/web/conc on the apps server and just the database on the other server.    Does anyone have any comments or suggestions, or issues that have come up from doing this modification for the upgrade?    When I