Ok yes I see what you mean by boxing the heart. That would work well. The stuff that I cut from logs with only an Alaska mill I take a 6in center slab right through the heart and then maybe a 2-4in slab above and below that depending on the size of the log.
Here's a good video showing how QS is done. This is a nice large quarter of Rosewood. Those first several cuts will be perfectly vertical grained and as they get further down they will start to be off quarter yet still considered QS. Again what we want is vertical.
https://www.youtube.com/watch?v=kansL2IZzW0