I am not certain what you want to do, but I am guessing you want to use a live center in one of your spindles to simulate a tailstock. Your picture appears to show a live center with a tapered shank and a gauge to show pressure. Yes, no? A straight shank would make chucking simpler. If you do want to simulate a tailstock, you will need a spring loaded center to be successfull. Some more details, please.