How to hollow a very complex part?

Hi everyone,

I've been trying to hollow out the following design:

However, the shell tool tells me that I am unable to create a thickness of .3 cm because an internal radius with a smaller value exists. I checked in the tools bar to find out what the size of this radius is, and it's incredibly small. I can't change the part as it is. Is there anything that I can do?

SolidworksParts And Features