Although it may be easier to build, it also makes it easier to break. Given, some of you may have used this style before, and it may have worked fine, but the way it's been mounted in the pic is asking to crack it. If you want to do a half-tube, rather than putting the wood 'in' the pipe, keep it out of it, and simply place the half-tube on a flat surface of wood. By putting the wood in the tube, its like having a wedge pushing two pieces apart (although in this case only one round piece.) This may be hard to understand, but the general jist of it is just keep the pipes full, because that's how they're meant to be kept, and that's how they'll be the strongest.