How about an easy way to solve your problem? Load the trailer and rear storage like you want to, leave the cement at home. Go camping this weekend and see how it tows. If the trailer tows fine which it should unless you go crazy with the weight in the rear storage area then problem solved. If by chance it doesn't tow so well then move some of the wood you carry to the back of the tow rig or front of the trailer, have fun camping and rethink the problem before the next trip. Carrying 600 pounds or cement for ballast is just crazy no matter how you look at it, if you need that much weight to balance out the trailer then one would need to rethink what you really need to carry while camping.
Can you use the ballast compartment for storage of the little used items?
