I haven't looked into that. I'd avoid trying to bypass a regulatory limit as that may not be legal (or considerate of other nearby wifi users).
There are the utf*.bin files... googling it seems these can be used to create a "testing" firmware-x.bin file (possible with the waltest.codeswap.bin). I haven't tried those either, but perhaps some of the board files are for testing.
I do recall a recent thread here in which it was observed that the stock r7800 firmware seems better able to cope with wifi interference on the 2.4 GHz band.
Perhaps some of the other board files are used to help with that.