I, for one, consider lowering the Sim 1 slots by 1 thousand right off the bat was a really bold move. If i was handling this and saw the screenshot below, i'd instantly take away slots from Sim 2 and add them to Sim 1 (mind you its not even peak time yet). What amount of time would provide the ideal insight? I'm not sure what the technical limitations are, but if you're able to mess about with the slots easily, there's no reason why you shouldn't do it.
And to answer the person above me, if things were bad 2-3 years ago, they don't have to be bad now as well.