good tips overall but DO NOT GLUE THE 2 HALVES WITH EPOXY
!! The Epoxy will most surely melt the EPS foam while it is curing and even if it doesn't you'll end up with a sort of epoxy "stringer" in the middle of the board which will alter it's flex caractheristics.
Glue the 2 parts using a RIGID POLYURETHANE FOAM SYSTEM and clamping them together very tightly. If you can't get your hands on a good marine 2 component urethane system use one of those PU spray cans they sell at DIY stores. It's still a lot better than using epoxy resin.
After you glue the 2 parts together sand down the whole joint and an area of at least 3 inches each side of the joint. Then you have 2 options:
1 (cheapest) - just laminate the whole strip with Epoxy and at least 3 layers of 4oz cloth, sand, fair and paint
2 (better) - sand through the pvc sandwich and vacuum laminate a new sandwich strip and laminate with epoxy and carbon fibre plus 1 layer of 4oz cloth, sand, fair and paint
option 2 is the sensible one and you don't need any rods for reinforcement.
If you're gonna do this yourself, like the chipmunk suggested, take the time to read through Eva Hollmann's web page: http://www.boardlady.com
There's lots of good info there.