[MechEng83]

Another thought on how to alleviate diminishing returns:
The point value of a scored tube increases by 1 point IF AND ONLY IF the row above it (left or right side, independently) is full.

This would result in normal scoring for the top row, and then the 2nd row would be worth the normal two points per tube unless there aren't any available pegs above -- then it's worth 3 points per tube. Bottom row would be 1 point per tube unless rows 2 and 3 are full -- then it's 2 points per tube.

All ubertube and logo doubling would still apply!