Would that be about 25" of draw on a long string? Hard to say cause i never measure tip movement. While it is true that if you want a heavy bow, brace it as soon as you can, at the same time some people (me for example) take this too serious and brace the bows when they are 150-170 pounds.
What kind of draw weight do you want? Can you compare some lower weight longbow with long string, to get a feeling in what poundage are is the warbow? I would try that, since its not really convenient or fun to brace a 150 pounder if you want 120 pounds.
You could also measure the mass of the stave and use Gardner's mass principle.