To be fair I used a simple Java program that you just input the hints you get and it spits out the left over numbers and a best guess (which is the middle number). Really on the 5-guess chests I was guessing after 2 hints to narrow it down, on the 6-guess chest I could open those almost always. The nice thing is it doesn't matter which type of chest, the torque can come from either.
OMG, call the GM! Seriously though, I'd hardly call that cheating Wint, it's just less work than doing it in your head, which is what I normally end up doing. However the point I start guesses at depends on the hints. If I know I can find an answer with the number of guesses I have left (number of possible numbers has to be <= (2^Guesses)-1 for me to start guesses), then I'll do it, otherwise I use the hints until I get down to 1 guess, at which point I take a stab at any of the remaining numbers.
With 6 guesses though, you should be almost always able to open the chest even without hints, although getting a good hint does make it a lot easier. A "good" hint is something like "the first digit is 3, 4 or 5", it's knocked out 2/3rds of your possible solution space. A "bad" hint is something like "the combination is greater than 29 and less than 60" after you've already had the first hint above, i.e., it adds nothing to the solution.