All that dead-space will be a problem. You'll be flushing enzymes out of the grain that will then sit in the dead-space and not do anything for the mash.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk