What difference does it make to the draw and how the bow shoots if it has stiff Siyahs or working tips? That seems to be the main difference between the various bows I've been looking at
The theory behind stiff siyahs (static recurves) is that the string angle remains low, which means that you get a 'gears' type effect as you draw and that effect stays more because of the stiff siyahs. The bow should therefore 'stack' less. Stacking, in case you don't know, is when the draw weight increases rapidly towards the end of the draw. For example, a bow might have a draw weight of 28lbs at 26", 30lbs at 27", 35lbs at 28" and 42lbs at 29". This is stacking, as opposed to increasing at a fairly steady rate. Most bows stack to some extent but stiff siyahs shoud keep it low.
What this means is that a bow of a given draw weight will not be gaining weight late in the draw. This in turn means that it must be gaining that weight early in the draw and therefore the total energy stored in the bow at full draw is higher (you've been pulling hard the whole way).
In theory, more energy in the bow means more energy into the arrow, and therefore more speed for a given arrow mass.
Unfortunately stiff siyahs are often massive and heavy. This means that they don't travel very fast. The energy transferred into the arrow is limited by the speed the arrow will travel at, and that will be limited by the speed of the limbs.
What you get instead is a relatively slow arrow and the excess energy just jars your arm ('handshock').
What you really want in a static
recurve is siyahs that are rigid but light. Let me know if you find one...