Bear,
I don't have much trouble if any getting them cured to the center. Here's why: I make up a curing brine, then pump it into the middle using a Cajun Injector clone. My goal is to have a fairly moist product, so I don't dry cure it. Dry curing would take longer even for a small piece like this. I have dry cured pork loins in the past and have also dry cured the outside with a bit of pumping for the inside.
A couple tips: 1. When pumping, make up the brine without spices or colored ingredients like molasses. Pump, then add these ingredients to the brine that you use for the outside of the piece. I learned the hard way that the spices or colors leave funny looking streaks on the inside.
2. I always use sodium erythorbate in curing mixtures. You certainly don't have to but it cures much faster as long as the cure can reach the meat. Plus the color resists fading better in long storage. Supposedly it also protects against nitrosamines if you're worried about that. I'm not particularly.
I can post the recipe for the brine if anybody wants it. This piece was glazed with a bit of molasses, sugar and pepper before smoking, too.