Modified Secret Heart Box

A slight modification from the Secret Heart Box adding a shelf along the inside of the cleave line on the top layer. This avoids the problem of filaments pulling the edge out of shape if the first fill is anything other than in the X direction.

My worst problem for the original Secret Heart box was in the bridging for the top piece. It appears that many are printing with PLA and with aggressive cooling that seems to work really well. I wanted to get ABS to work, and the one remaining problem