The most common hardware to send Midi notes to the plugins is the 4-octave keyboard. When i build sounds i tweak them in a way that they can be played nicely on such a hardware.
When you use a 4-octave keyboard the tuning of +1 octave works well for building sounds of these categories: lead, keys, pads. Furthermore a setting of +1 is closer to the Midi standard. +0 octave works well for bass. Of course there is no law that forces you how the tuning must be. Just use the tuning which works best for the patch the you currently are building.
To build own init patches you could do this:
1) Create a new directory in Icarus_sounds like MyInitPatches
2) Restart Icarus to force a rescan of the patch categories
3) Init a patch. Tweak it in the way you want
4) Store your own init patch in MyInitPatches as MyInitPatch1.fxp
Best Regards,
Markus