mem_init_install with a half rate bridge

I have an SOPC system that contains a DDR SDRAM HPC and a half rate bridge adapter, plus a NiosII and a bunch of peripherals. The bridge adapter is the master to the DDR HPC while the Nios and a couple other peripherals are masters to the bridge adapter.

I'm trying to compile a BSP with the --default_sections_mapping argument to identify the SDRAM as the region to put all of the code. The BSP tools don't recognize the SDRAM as a region because the bridge adapter is in there (I'm assuming). If I set the bridge adapter as the --default_sections_mapping target, the BSP and application software will build, but the mem_init_install target won't generate a .dat file for the SDRAM for simulation.

Anyone know how to make this work?