I would also like this. While I can java number crunch using (float) to obtain a real number, the stack viewer refuses to add them using sum(propertyName). Works with Integers, just not real numbers.
Alternatively, can the Summary text above pieces area be made a beanshell expression area. With this ability, I could still use the existing sum(propertyName), but I would deliberately multiply that propertyName by 10 so the sum function still uses integers and then I divide the sum(propertyName) total by 10 within the stack viewer Summary text above pieces area to get what I want to be displayed.