Doubt it, that 10 inch one looks to be about as large as will fit, looking at clearance on the top and bottom.
As above, the opening under the brace is only 11inch high, I imagine the only way would be to intrude on the spare wheels well. And be willing to cut your carpet. The sub would be partially hidden!
The only other option would be to build a box that fits in the space on the front side of the brace, not quite sure without measuring up etc...