chi80,
in regards to psp-290 - I am not sure if you can load required prx files under 1.5 kernel. At least it never worked for me...
Building a 2.++ compatible eboot is no brainer..
You just need to change a few things in the make file ( see my latest source code )
You may have problems linking your c++ libraries, though.. Well, I can't tell you more without looking at your source code..
You can attach your packaing format specifications / sorce code to this thread so in7ane and myself could evaluate it's efficiency..