I think what you are referring to is a rack lockout. But going a little deeper. Instead of those i would do board presses. If your not familier with them there 2x6's cut them about 18 inches long and nail 2 or 3 or 4 or even 5 together. Each board is 1 1/2. The reason i would suggest these is number 1 you can stay in your bench groove better because you un rack , lower pause shoot to lockout. Number 2 in my opinion nothing will strengthen your lockout better then these. Your shirt will help you with the bottom. But if you want to try rack lockouts or half presses, the only think i dont like is finding your groove at the bottom of th elift. Now thats if you start with the bar in its lowest position. Finding groove , and over coming enertia are the downs with those. So if you do them i would un rack like normal lower to the pin then push back up. The real difference between these and boards is when you reach the bottom you will hit the board evenly, with pins you come down , one side will bang first it gets messy. But people have been doing them for yrs i would only go as low as 5 or 6 inches then pop back up. To much lower, considering you will be using a higher weight, seems like you expose your self to injury. If you only do bench work once a week do them after you bench. If you bench one day and do assistance work again on another day they would be first on the second day.