I suggest buying Alpha khakis directly from Dockers.com. They waived the return shipping charge on everything I bought that had inconsistent sizing. What they lack in quality control they have made up for with customer service for me.
So far my experience is the buckskin color is the most inconsistent. I have found they also stretch out a fair amount, in the seat and waist mostly. Don't pay retail for them but they are always 20-30% off anyway, worth it at that price for me. FWIW they fit me pretty good and I'm 5'10"ish and 140lbs, so yeah pretty slim.
Dockers and Levis, the same company afterall both have serious sizing issues. I have 3 or more pairs of 514 jeans and they are all over the place, they vary by several inches in length, waist and thigh/leg measurements.