You could try using transition jumpIn' which, according to documentation, makes the change effective in the number of cycles specified as an argument, at a cycle boundary.
So, here, since from what I understood you don't want to wait before the transition (ie make the jump in 0 cycles), you're gonna want to do
(jumpIn' 0) 1 $ stack [ n "0*4" # bd, n "[~ 1]*2" # sd ]