That's why I like to weigh them, with some baby corns it seems they grow longer first and then fatten up, while others it seems they fattem up first and then get longer.
The ones who fatten up first are probably better candidates for the munson plan, while the ones who get longer first will probably take a little longer before you up the size they're on.
This is just from watching the corns grow at a local store though, so pure conjecture. My corn is around 16 inches atm, 15g I figure when they reach a point of 1g of weight per 1inch of length it might be worth looking in to upping to two pinks, rather than following the munson plan precisely i'd rather wait a little longer before going up a size than go up a size too soon, risk a regurgitation and then have to wait even longer to go up a size.
Hence why i'm taking length / weight each month... and to track growth.