Roman Numeral D20

I wanted to do a unique D20 for my brother, who is big into D&D. I thought roman numerals were interesting, so I am trying this new design.

The first print went alright. the bottom portion of the print leaves something to be desired. The triangular faces on the bottom half came out concave, and despite the .25 infill setting, the thing is nearly 100% solid ABS.
I think I might be able to solve both issues on a future edit and re-print when I'm home again if I make the model itself somewhat hollow.