i'm sure you already found the answer despite at such late reply. if that's not the case... here it is:
you may set INVENTORY_BASE_SIZE to 150 then re-compile. It works, it's just the inventory display wrong because of hard-coded client site. you can patch client and set the maximum inventory base on your mmo.hpp setting.
please beware that the total of MAX_INVENTORY never go exceed at around 250 due to the 'packet size'? else your server would freezed out of existent.