Well yeah, that's the problem I bet. If you don't hollow thicker models like this the sunlight or other UV won't be able to reach to the inside during the post curing. So you've still got liquid resin inside there. It's also just a waste of resin if you don't hollow it.

I actually just posted a video on supports and talked about hollowing in the beginning.
https://youtu.be/4duyDAP6a2c