Modding Alexander campaign, different than vanilla?

This is a question for modders who had modded Alexander's campaign map and region.

I'm having problems adding a 4th region/province. To make things simple, I made the entire map into 2 regions only and it worked ok. Added a 3rd, fine. Added 4th, CTDs with no message. It doesn't matter what the name and the location of the 3rd region, it works. But adding another region would CTD the game, even if the 4th region was working as a 3rd.

I thought it was my scripting so I asked Makanyane, who tested it with vanilla 1.5, and it worked with 4 regions. So I'm going to assume this is something unique to Alexander's set-up.

So can someone point out what is different with Alexander's map system than vanilla's?

Thanks.

Whooop, I got this solved by a dding a LOT of regions. The problem was most probably land mass ratio.