Geezer here: I have had some experience with goats foot (gafa) levers. In the illustration above, you can change the geometry by three means... either lengthen or shorten the hooks that grabe the string, lengthen or shorten the 'legs' that fit over the gafa-pin behind the lock, or move the pin itself. I suggest making a thin wooden mock-up to establish what works best. Period bows that use the gafa normally mount the thru-pin about 2 inches behind the lock. Usually the pin lies near the top of the stock, but some English 'latch' type bows use a combination trigger pin and lever- pin, and mount it near the bottom of the stock. I can see some advantages in putting it low, but haven't tried it myself.
When you actually Use the lever, you'll draw the string behind the lock (it will appear to be too high... you can't possibly get the string into the lock there, but when you let the lever rock forward again, it will drop the string neatly into place.
Maximum draw weight for a 'gafa' bow? I figure about a 5/1 leverage, so say a maximum of around 500 lb. draw without strain on your body. Geezer.
Note one of the biggest problems with goatsfoot levers is actually string-wear where the lever hooks on. Either make your hooks very wide and smooth, or figure on extra serving on the bowstring where the lever makes contact. Geezer.