Typically, as you move down your seat should move back to help your balance. Remember, that as you move your saddle back, you are increasing your reach to the pedals, and will most likely need to lower the saddle slightly, too. This all should be in very gradual increments; think millimeters. As to weight on your hands: This should be pretty mild. You should be able to ride in your neutral (home) position with a relaxed upper body and as a rule, be able to lift your hands from the handle bar without falling forward. Core strength is a
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A few notes:
- Balance in position is mostly controlled by the saddle fore/aft positioning and saddle tilt.
- As a general rule, The further forward your saddle is the more weight goes on your hands. The same is true of tilting the saddle nose down
- A good starting point, is to set the saddle level, or with a slight (~1 degree) upward tilt and figure out the saddle fore/aft and height first.
- Core strength is also (very much) a function of balance. The stronger your core, the more your torso will tend to suspend itself and the more leverage it gives you against the pedals. This means that the stronger the core is, the less weight is supported by your hands.
- As the core develops your fit will need to change slightly to optimize this new strength. For a lot of people, that make a preference for a lower cockpit relative to the saddle. This is also dependent on riding style and the proportion of the rider.