Had the country continued along the original design, we would need a stadium just to hold a congressional meeting; just not feasible. Currently, the census uses updated population figures to balance out the representation per state, some states gaining or losing seats every ten years based on population trends. It's major flaw, imo, is that it doesn't limit itself to citizens, counting everyone who dwells in a state, citizen or not. This robs citizens of representation in heavily populated areas where non-citizens live...Cali, for example. Cali, based on it's illegal immigrants alone, has 6 seats that should legitimately be given to other states, but that's something else altogether.
Having 13 districts courts serves the greater need of the population and helps with backlogs. Adding more SOTUS judges does none of that.