It's another winner Max! I'm a big fan of that particular type of cone too. I use those alot myself because i like the effect they give off with the tight bottom and then quickly the leaves stem further apart.
I know when i make them, I trim them, otherwise it would eat up too much resin. I use a 7/8 wide mold. I trim them so they fit nice and snug down in the mold. I do not worry about if the core is very centered. I fill the mold with alumilite mixed with whatever colors and stuff and pressurize at 40 Lbs. That's it. Usually can't tell where the center is and don't really care. I think they actually look better when you drill off center revealing part of the core on one side of the pen. It's quite a simple process and pine cone pens sell well! BTW..that's two pine cones I see there. They are real fat and tight on the bottom and taper fast to a point where theres very few leaves. He has them so the tips are facing each other. You can use any type of pine cone and they all give different effects.