#1. Dad's ratty old singlet may be free but the bad fit loses much of the 'spineliness' in translation.
#2. Make holes more 'spinely looking', ie. less like a bunch of pebbles stacked up on each end.
#3. Don't forget the subtle curve to the spine.
#4. Consider doing a rib-cage cut out tee. Technically speaking, it's totally possible.