I am also using XOOPS for my business. Although I am not a programmer, I was able to modify it to fit my needs (most of them). For example, I pretty much altered the Sections module. The only trace of it being the section module is by the URL for it. (modules/sections/)

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Although it isn't a "huge corporate" business, none the less, it is a business to say the least. I am finding the one type of site this system seems to be hard to outfit for are gaming groups (squads,clans, etc.). I am currently working on extreme modification to get that down.