A sequential fourth generation is still viable, but the t 0 and b 0 quarks are constrained not to be too far apart in mass. The t 0 ! bW and b 0 ! tW decay channels are still being pursued at the Tevatron, which will soon be surpassed by the LHC. We use a convolution method with up to five-body final states to study t 0 and b 0 decays. We show how the two decay branches for m b 0 below the tW threshold, b 0 ! tW à and t à W, merge with b 0 ! tW above the threshold. We then consider the heavy-to-heavy transitions b 0 ! t 0ðÃÞ W ðÃÞ (or t 0 ! b 0ðÃÞ W ðÃÞ ), as they are not suppressed by quark mixing. We find that, because of the threshold sensitivity of the branching fraction of t 0 ! b 0 W à (or b 0 ! t 0 W à ), it is possible to measure the strength of the CKM mixing element V t 0 b (or V tb 0 ), especially when it is rather small. We urge experimenters to pursue and separate the t 0 ! b 0 W à (or b 0 ! t 0 W à ) decay in their search programs.