Add bass when water temps drop into the upper 70's, probably late September, early October. F1's will be great...if you can find them. Be specific when asking questions of your supplier. Enquiring minds want to know.
Regarding culling, the fish will tell you. Originally stocked fish should grow fast. Their babies will likely be the ones you will cull. Next spring, a percentage of bass you stock this spring will spawn. Then, next fall, you will begin catching young of the year. Recruitment essentially allows the population to replace fish, or to fill an unused niche. As your bass grow, watch their lengths, compared to weights. When your bass begin to show signs of weight loss, that's the signal to cull. You may want to read our book, "Raising Trophy Bass". It explains how to do it. Want "balanced" fishing? Harvest a balanced bounty. What you need to figure out is, "What is your bounty?"