Veldt packs hacking

I was just wondering if anyone ever changed the formations that you meet in the veldt? As we all know, thee are 64 packs with 8 formations in each. Some are empty or contain only a few formation. I would like to change some formation from a pack to another or simply add/remove formations to a specific pack.

I know they are two requirment for a formation to appear on the veldt. First, the formation number must be below 300 something (I don't remember the exact number) and you must have cleared the formation in the game.

I had a look at the ROM map but haven't found where the data concerning the veldt packs is stored, especially the data of which formations are in the 64 packs. Has anyone ever played with that?