From the factory is the steerer tube on the Trek 520 long enough to get the bars to seat height? Is the tube cut to length at the factory or is that done at the bike shop? Is there a safety issue with regard to the steerer tube when setting the bars high?
My 520 came with the steerer tube already cut. I talked to the LBS beforehand about it, and they said that there would be no problem with setting the handlebar high enough (seat level.) For me it turned out to be true. The stem that came on it was angled up enough to place the bars just below seat height. I later decided to have the bars up a little more, so the shop swapped out the stem for one that angled up even more. They said if I wanted even more height that they could achieve that with an extension of some sort.
I don't know if there are any safety concerns with the bars set higher.