plug made.. mold made.. now what

the back usually

 

There are only 1 or 2 cores that should be used in hull bottom(my opinion) Core-Cell and Airex. Look at the following websites. http://www.hightechcomposite.com/the_process/6_finished_product.htm These guys have been using core-cell in the bottom of offshore race boats for ten years and they know what they are doing. If you do not have the time, skill, or resources to "properly" vacuum bag the core to the laminate, you should not use cores in your boat! Heres a boat using Airex in the hull bottom. http://www.dragonpowerboats.com/
This boat is built by Hightechcomposites at the previous website. Again, these boats are vacuum bagged every step of the way. There built using epoxy with a 14 hour cure window. I know this because I used to work there. Lastly, here is an article from yachtsurvey boasting about the properties of Core Cell. Like buckknekkid said, it comes down to the skill of the crew.