FWCalendar is fully scaleable. Just change the margins in the preferences file and run the macro; a proportionally scaled new calendar will be generated. There is no need to change font sizes: a calendar rendered to fit in a 7.5" x 10.0" space will look essentially identical to a calendar rendered to fit in a 1.875" x 2.5" space.
The Pagestream version is completely scaleable. Because Pagestream allows fractional font sizes, and font sizes from 1 pt to 50000 pt in 0.001 pt increments, you could theoretically print a 0.79"-high calendar that would look just like a 7.5"-high calendar. Obviously printer limits come into play before Pagestream's font-size limitations.
Final Writer has a lower limit of 4 pts for allowable font sizes, and font sizes must be whole numbers. This limits the vertical size of FW-rendered calendars to no smaller than about 3.125". Although small calendars will appear proportional to larger calendars, the text sizes may be slightly different.