1RB1RF_1RC1RA_1LD1LF_0RB0RE_---1LC_---0LC

1RB1RF_1RC1RA_1LD1LF_0RB0RE_---1LC_---0LC (bbch) is the current BBu(6) champion halting after 16088 steps

Analysis

A(x) = 0^inf <C 1^x 0^inf

A(3x) -> A(4x+3)
A(3x+1) -> halt
A(3x+2) -> A(4x+5)

A(2) -> A(5) -> A(9) -> A(15) -> A(23) -> A(33) -> A(47) -> A(65) -> A(89) -> A(121) -> halt

If B(x) = A(2x+1), it's trajectory is equivalent to the BBf(20) champion