A suggestion for an additional "rule" in HARP: when a group of people is performing some sort of collective effort ( spell ritual, searching a secret door, etc.), there needs to have some mecanics to account for all the skills those people "bring" together.
So instead of having every character rolling individually (e.g. Perception when searching), one roll is made by the character with the highest skill bonus, and the other ones give a bonus on the roll.
There is something along those lines in the Herbs & Poisons chapter (united Group Searches). I made a quick search in the book and couldn't find anything more general, though the way it's written, I think it could be used for any other skill.
If there is already a rule for this kind of situation, sorry! (But please, give me the reference where I can read it!)