I realize now that I probably should have circled the entire bolt hole on the end rails under the valley pan, but I was trying to minimize the amount of RTV that could make its way inside the block. I'll do some cleaning and seal the bolt heads from the top to try and stop any oil seepage that may come up through the bolt hole. It's possible that enough of the RTV squished around the opening, but damn, this is one of those little details that will nag at me for a while.