I set a Schedule Constraint of 24 months. Why does the Solution Panel show a 22-month schedule for the life cycle?

There are several reasons this could be happening, but the most likely cause is that you entered a target probability of more than 50% for the Schedule constraint. For example, if you enter a time constraint of 24 months at a target probability of 90%, you are asking SLIM-Estimate to calculate a risk-buffered solution that provides a 90% probability that the project will not exceed 24 months: in effect, a risk-buffered solution.

The difference between the expected solution of 22 months (50%) and your constraint of 24 months (90%) represents the built-in risk buffer that protects you against possible size growth, lower than estimated productivity, staff availability issues, or other facts that may affect the delivery date. The size of this risk buffer is determined by the uncertainty range around the estimated size, PI, and manpower buildup.  The Solution Panel always displays the 50% solution because it is the work plan.

If you want your solution to correspond exactly to your input constraint values, use desired probabilities of 50% for those constraints.

How can I change the unit for Total system size in the Balanced Risk and other solution wizards? Currently it is set to IU, but we use Function Points.

Solution wizards that require a size estimate assumption use the Sizing By History technique to obtain an initial "ballpark" estimate based on the statistical size ranges, or t-shirt sizes, in your project's associated trend group(s).  This technique uses the Function Unit and Gearing Factor in the Project Environment settings.  Most of the templates installed with SLIM-Suite have the Function Unit set to the Base Size Unit, either IU or SLOC.  

To change the Function Unit to Stories, Features, Function Points, or other size unit, select Tools | Customize Project Environment from the menu. On the Project Description Tab, there is a Function Unit list box.  Select Function Points or other unit, then enter an appropriate Gearing Factor to represent the average number of Base Size Units (elementary programming steps) contained in your selected  Function Unit (ex.: a gearing factor of 50 represents 50 Base Size Units per Function Point).  

If you need help determining an appropriate gearing factor, visit the Function Point Gearing Factors page on the QSM web site, download our Gearing Factors whitepaper, or contact QSM for assistance.