Dlennard,
You are exactly right. When you hoist the jib, the wire luff on it becomes the new forestay and it pulls the mast forward considerably and tensions up the whole rig. You'll notice a fiddle type block at the bitter end of the jib halyard and a cheek block mounted to the mast. Rig these two up with about 20' of 1/4 inch line and hoisting the jib/tensioning the rig will be a snap. If you want to sail jibless, you'll have to add some sort of other line or wire stay to tension up the rig with.
jrg