After rolling up a few pc's, I think I'll go with 3d6 in order but count 1's as 3's. This gives a spread of 6-18 and weights the scores heavily to average. Here's a few that I rolled up-
17, 8, 9, 11, 14, 11, 12, 10
8, 14, 12, 11, 11, 11, 12, 10
13, 11, 10, 11, 12, 14, 9, 14
9, 11, 13, 14, 12, 13, 16, 10
All very playable without being supermen.