If you are making the tail stock ahead of time, cut the sections of tail you'll be using a bit longer than you want. While stored, even for a few days, the plastic exudes some oil that if left on the tail will hinder the welding when the body color is injected. Rather than messing with bonders just trim the tails to length as you need them. I have bags of tail stock for the full line of Thump-Its, Rippers of all sizes and some Kietech Baits I make and all of these tail pieces are at least 1/8" longer than I need. In the bags they are oilier than heck. When I am going to make baits that call for those tails I count out what I need and trim them and use them right away.
Also, if you are injecting a firmer plastic for the tails, add stabilizer to your body plastic and inject the bodies at about 170 degrees and hold pressure on the injection after the plunger stops....5-6 seconds