improve algo to prevent parallel words with no overlap

[petermeissner]

. 1 2 3 4 5 6 7 8 9 0 1 2
1 # # # # # # # # # # # #
2 # # C R A B # . O B M #
3 # H # P U G # . X A O #
4 # A . # B E E # # T U #
5 # M # S A L M O N # S #
6 # S . E # C O Y O T E #
7 # T # A L P A C A # # #
8 # E E L # T U R T L E #
9 # R H I N O C E R O S #
0 # # W O L F # # F O X #
1 # K A N G A R O O # . #
2 # # # # # # # # # # # #

... e.g. Crab and Pug run in parallel with no overlap whatsoever ... algo produces a lot of those