but love science when it finds uses for hemp
Because with large scale hemp agriculture, you can always sneak in a few rows of 'the good stuff'.
No, you can't - although the belief that you can is apparently what has kept the hemp business shut down in the U.S. for 80 years (and led to Governor Arnold to veto a hemp cultivation measure in California.
The cultivation patterns are completely different. The hemp crop is grown in dense plantings that lead to tall stalks and few leaves, and then the crop is either harvested before it flowers (if an all-fiber farm) or is allowed to go to seed (if hemp seed is also harvested).
Either way there is no way that a successful drug crop, however small, can be snuck in there. (Not so drug cannabis and, say, field corn though - hiding pot among corn is an old trick).