I have never been any good at peening a dovetail sight to get it tight. I've resorted, successfully, to adding a thin skin of JBWeld to the bottom of the sight then filing it smooth the next day until it just goes in with light tapping with a punch and small hammer.
"I come from a state that raises corn and cotton and cockleburs and Democrats, and frothy eloquence neither convinces nor satisfies me. I am from Missouri. You have got to show me." Willard Duncan Vandiver