Well, my tiller tree only takes up 576cubic inches, which isn't much in my 16'x28' basement shot. To me, that's not a lot of lost space. I normally keep more shavings on the floor than that. If we all could take bow building classes from John Strunk there would be no purpose for this section of TradGang. But, unfortunately we all can't.
For the average guy trying to build a wood bow, the tiller tree is a valuable tool that will help him achieve tiller safely.
My tiller tree is a 2x4, bolted to the basement wall. It has a block on the top that the bow's handle rests on and a 10' nylon rope with an "S" hook that will attach to the bow string. The rope goes down through a pulley at the bottom of the free. This will allow you to stand back 6' or so and as you pull the rope, you will be able to see the bend of the bow.