Good read. Historically, batsmen effectively average 2 runs more per innings once they get off the mark. So, their conversion rate from 50 to 100 should be, on average, exp(-50/(avg+2)).
Using that formula, Chanderpaul's expected conversion rate is 39.18. So he did indeed underperform his expected conversion rate.
I have gone ahead and updated the original graphic to include each batsmen's expected conversion rate.
*Click image to enlarge
As we can see, there were some big name players that had a below expectancy conversion rate, including Kanhai, Richards, Lloyd, Haynes, Chanderpaul, Butcher, Worrell, Gayle, and Fredericks.