Custom Field Limits

Custom Field Limits

Hi,
I really need to have 9 custom field of type 'Dropdown' for Customer object to let customer chose some options from limited set in Customer Portal. The problem is that I cannot create more than 5 Dropdown. I get message:  Please check the following
  • Youve reached the maximum limit for the number of custom fields that can be created for this data type. 
Please let me know if I can add more of them somehow. Also it is unfortunate that the limit is nowhere specified. 

Thanks,
Marcin