What lbs test for a Penn 9500 SS

What pound test should I put on my Penn 9500 SS. The rod is a 10 foot Ugly Sick. Yes I know its overkill for Kings and the rod is too long for the pier. I had success with kings in years past with it, but the locals probably ducked when they saw me coming. I would target redfish or whtever in that size slot. I want to stick with mono. I should probably put 15 lbs test on it. the reel should hold over 400 yards?

Thanks to the good people at J&M. They shipped me a rod and reel to my home in Cincinnati. They packed it so well it took 15 minutes to get all the protective wrap and foam off it. I got a great King combo. A 8 foot Gulf Stream Pier rod coupled with a Shimano 8000 Baitcaster. I have to be content to fish the Ohio river for catfish until I can get down there in September. It's so pretty I am going to hate to lay it on the river bank.

I have one and put 25 or 30 on it. I'm thinking you'd have casting issues with line that light on a reel that big.