One of the file type options in the Biab injector is to use flac, Reaper will batch convert all the RT/RD wma or wav source files to flac and inject them directly.
There is also a wavpack .wv option that you can encode the BB multitrack drum stems in Reaper to a single multichannel file that it will inject into one track. I think the flac only supports 8ch whereas wav or wavpack will support many more.
You could also have multichannel ogg

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