Ok, so if I increase HD and thus add 2 size categories, help me understand: Diminutive to Tiny adds +2 Str, -2 Dex, then Tiny to Small adds an additional +4 Str, -2 Dex, for a total increase at the end of +6 Strength, -4 Dex, correct?
If you use Herolab, the program doesn't allow the Giant template to be applied twice, but it does allow you to add any number of "Size Increases" to the creature. Making a size Small Sprite was no problem with the program.