Back when I wrote that program, I did so because I had tried to find a consistent ratio for shed skins and my conclusion was that there is no consistent ratio.
Sunny, my amel motley, just shed this week. She measures 34 inches, and her shed skin has now dried enough to be 34 inches long, and that was when I stretched it to the point where it ripped. Based on that instance, it would be more accurate to measure the shed and just take that exact amount.
If it's very important to be accurate to within a very small amount, I would suggest taking an x-ray and measuring it from there, because it is not skewed or fisheyed and you can measure it very easily and accurately.
My program is mathematically sound, but it also depends on the user being able to use it properly, and tends to take a lot more effort compared to the other methods.
In my experience measuring sheds is dependent on a lot factors that are beyond control and can't necessarily be quantified and measured. The length determined from that method depends on the "age" of the shed, how much you stretch it (and possibly how fragile it is at that time) and it can also depend on how much the snake stretched it out while shedding it.
Use whatever method you want and be happy. But given how much the results can vary, it certainly would not make sense to use it in determining a record for the longest cornsnake.