Part of making sure our search engine 'cognitively fits' means we have to respect how we're all wired up.
We all have limited mental bandwith (for the moment) and a search engine should help you navigate through the morass of information by helping to manage your cognitive load.
In George A. Miller's classic psychological study (The Magical Number Seven, Plus or Minus Two) he found that we have a cognitive capacity for seven 'chunks' of information plus or minus two. We've all had to grab for a pen when taking down a phone number that's too long. Miller's, 'seven plus or minus two' rule explains why.
What does this mean for the design of Trexy? It's tempting to follow all the other search engines and show ten results per page. But Miller's rule suggests we're more comfortable handling less than ten things at a time. Imagine driving your car and coming to an intersection with ten exits!? It's crazy.
This is the reason why we only show five trails per search result - so they can comfortably fit - cognitively speaking!