as you very probably know, yeast is "alive" - it grows and multiplies. discounting "extremes" - using less yeast just makes the rising take longer - given time the yeast will multiple and do its thing. a bit more or a bit less is not going to make or break a formula.
I rarely double a bread recipe as most of mine 'fill the mixer bowl' - and I'm not uber-careful with the measuring of it - more or less a teaspoon works for me (g) - but if I'm going to plunk it in the fridge overnight I do cut back to about half a spoon.
too much yeast can cause an early 'over-rpoofed' condition - so in the case where you want to double the batch and keep half for later, there's a glitch - how to get a normal rise time for the first and a delayed rise for the second . . .
for more ideas & tips see:
Baker's yeast - King Arthur Flour
We’ve found that here in our King Arthur kitchen, where we bake bread every day, we can cut the yeast back to 1/16 teaspoon in a 3-cup-of-flour recipe and get a good overnight rise. In a kitchen where bread is seldom baked, we needed 1/2 teaspoon of yeast to get the same effect.
the best pizza crust I've found is Jamie Oliver's - bread flour with a portion of semolina -
Pizza Dough Recipe : Jamie Oliver : Food Network
I cut that recipe in half for two 12 inch pizzas.