WRT the stddev calculations - I seriously doubt that the curve is normal at the top. (For example I bet there are more 228’s than 227’s.) Also, as I describe below, what happens to scores in the middle seems to be different than what happens to scores at the top.
If you compare the recently released percentile tables (including the 99+), and map it to 2014, you might end up with the following as a way to convert your 2015 score into a corresponding one from 2014:
If your 2015 score is 228, add 12 to get a corresponding 2014 score of 240.
If your 2015 score is 214, add 10 to get a corresponding 2014 score of 224.
If your 2015 score is 205, add 8 to get a corresponding 2014 score of 213.
If your 2015 score is 202, add 4 to get a corresponding 2014 score of 206.
If your 2015 score is 200, add 2 to get a corresponding 2014 score of 202.
If your 2015 score is 198, add 0 to get a corresponding 2014 score of 198.
IOW, the higher your score, the more points you add.
This would imply that the CA cutoff is 213. (Because adding 10 gives you a 223, which was the 2014 cutoff.) Which is obviously at odds with the data you get from the concordance tables. (They imply much higher cutoffs.)
So - I think the percentile tables imply a 213 cutoff for CA, while the concordance tables seem to imply a 219 or 220 cutoff. It remains to be seen which one is more accurate, and/or why they disagree.