Keep in mind also that B3 from AF3 and F3 from UI3 are each only a GCD in cast time, whereas if you Transpose, the return to AF3 via F3 is going to cost you another .4 GCDs due to facing F3's full cast time, making the transpose only a .6 GCD gain. I'd only ever recommend it if you have at least 2 out of 3 among (a) Thundercloud, (b) Foul, and (c) lucky/early MP tick, and it's situational even then.