I lean towards cottontail distress most of the year. Bay Bee Cottontail on your Foxpro Spitfire is a good one, DSG Cottontail is another high producer (might not be on your Spitfire though).

We're getting into early breeding season, or at least will be soon if it isn't kicking off in your area yet. Male territorial vocals and female invitation howls will start producing better and better in the next few weeks.

I personally do not locate before I call a set. I don't want to draw any attention to myself before I am ready to call and kill one. The only time I locate is if I "scout" a spot the night before to be called in the morning. I'll locate around midnight to 2am (usually after running coons with hounds), just to see who is in the area. If 3 or 4 groups of dogs all around the spot answer, then I for sure come back. If nobody answers and I get better response elsewhere, I might not prioritize that set as highly the next morning.