Forum ratings for summed scales are counterintuitive

Based on slashdot's rather nice discussion moderation system, I wanted to grade my students based on the number of points they had gained from other students, so set the ratings to 'sum of all ratings'. However, If I give each student the ability to use a scale with only one point, the maximum any post can get is the top of the scale, i.e. one point. Not much use.

What is needed is a way to specify a maximum grade for the summed ratings which is higher than the maximum for the scale. Discussion on MDL-13804 suggested the need for an open ended grade with no maximum, but I think this is unecessary and undesirable.