AIX 5L+? Minimal porting? You've very obviously never actually done it.
The total extent of IBM's efforts with AIX 5L was to put RPM 3.0.3 on their systems and build a few RPMs. The underlying source base for your RPM better support AIX or you're in for a good deal of fun. And you know what? Pretty much everybody dropped AIX support years ago for, I might add, very good reasons. AIX is a Unix, but a seriously weird one. Oh, and by the way, can you guess the version of RPM shipped with the latest AIX? Clue: it begins with 3. Check out the versions of packages at http://www-03.ibm.com/systems/power/software/aix/linux/toolbox/alpha.html. Most/all are seriously old. Many are a decade or more out of date.
As someone who has to deal with targeting AIX (as well as Linux), from my developer PoV AIX is dead, dead, dead. And starting to smell very very badly.
Meanwhile, Oracle have something like, what, 28k system sales per anum on which to amortize the cost of SPARC development? Pity. I loved old Sun kit, but sorry, SPARC is walking dead too. Just like AIX and POWER.