Here is the Indiana statute that will govern commissions.
BTW, your source's history regarding the 1787 convention is AFU. The states were going to convene regardless of congress, and delegates were indeed limited, some more than others. Delaware's demand of equal state representation, resulted in the key compromise of two senators per state.
If you wish to compare a state amendments convention with a familiar institution, compare it to the electoral college. Both are federal rather than popular, and are/will be limited by state law. If the states are so politically insane, why haven't we had a 'runaway' session of the electoral college?
I keep getting back to the idea that doing nothing is not an option.