I have the same question as you do and hopefully someone will answer it.
I did find a solution to part of this in a different discussion thread. According to "Kate":
"I've managed to do this by editing the following line in the whform.js file in the Webhelp output folder:
var gnMaxRslt = 10;
It's a bit of a pain to do this every time I compile, so if anyone knows how to achieve the same result without reverse engineering I'd love to hear from you.
Also I edited whfhost.js so that the Rank column in the search results doesn't take up 50% of the space and it looks a lot better."