These are some example grids that I used to experiment with exact cover problem solvers. They are minor spoilers for some of the puzzles, since you will see the puzzle grids.
9x9 front grid
...#..... ...#..... ...#..... ......... ###.#.### ......... .....#... .....#... .....#...
9x9 back grid
...#..... ...#..... ...#..... ......### ....#.... ###...... .....#... .....#... .....#...
11x11 front grid
....#...... ...#...#... ....#...... ........... .##...#...# .....#..... #...#...##. ........... ......#.... ...#...#... ......#....
11x11 back grid
......#.... ...#....... ......#.... .......#... .##...#...# .....#..... #...#...##. ...#....... ....#...... .......#... ....#......
13x13 front grid
....#...#.... ...#....#.... ........#.... #...........# ....#....#... .....#....##. ......#...... .##....#..... ...#....#.... #...........# ....#........ ....#....#... ....#...#....
13x13 back grid
....#...#.... ........#.... ........#.... ##........... ....#....#... .....#....### ......#...... ###....#..... ...#....#.... ...........## ....#........ ....#........ ....#...#....
9x9 DLX (5177 lines)
Here are the first 10 lines of the DLX file I generated for the 9x9 pair:b_0_0 b_0_1 b_0_2 b_0_4 b_0_5 b_0_6 b_0_7 b_0_8 b_1_0 b_1_1 b_1_2 b_1_4 b_1_5 b_1_6 b_1_7 b_1_8 b_2_0 b_2_1 b_2_2 b_2_4 b_2_5 b_2_6 b_2_7 b_2_8 b_3_0 b_3_1 b_3_2 b_3_3 b_3_4 b_3_5 b_4_0 b_4_1 b_4_2 b_4_3 b_4_5 b_4_6 b_4_7 b_4_8 b_5_3 b_5_4 b_5_5 b_5_6 b_5_7 b_5_8 b_6_0 b_6_1 b_6_2 b_6_3 b_6_4 b_6_6 b_6_7 b_6_8 b_7_0 b_7_1 b_7_2 b_7_3 b_7_4 b_7_6 b_7_7 b_7_8 b_8_0 b_8_1 b_8_2 b_8_3 b_8_4 b_8_6 b_8_7 b_8_8 f_0_0 f_0_1 f_0_2 f_0_4 f_0_5 f_0_6 f_0_7 f_0_8 f_1_0 f_1_1 f_1_2 f_1_4 f_1_5 f_1_6 f_1_7 f_1_8 f_2_0 f_2_1 f_2_2 f_2_4 f_2_5 f_2_6 f_2_7 f_2_8 f_3_0 f_3_1 f_3_2 f_3_3 f_3_4 f_3_5 f_3_6 f_3_7 f_3_8 f_4_3 f_4_5 f_5_0 f_5_1 f_5_2 f_5_3 f_5_4 f_5_5 f_5_6 f_5_7 f_5_8 f_6_0 f_6_1 f_6_2 f_6_3 f_6_4 f_6_6 f_6_7 f_6_8 f_7_0 f_7_1 f_7_2 f_7_3 f_7_4 f_7_6 f_7_7 f_7_8 f_8_0 f_8_1 f_8_2 f_8_3 f_8_4 f_8_6 f_8_7 f_8_8 b_0_1 b_0_2 b_1_2 b_1_1 f_0_1 f_0_2 f_1_2 f_1_1 b_0_1 b_0_2 b_1_2 b_1_1 f_0_1 f_1_0 f_0_0 f_1_1 b_0_1 b_0_2 b_1_2 b_1_1 f_0_5 f_1_4 f_0_4 f_1_5 b_0_1 b_0_2 b_1_2 b_1_1 f_0_5 f_1_6 f_0_6 f_1_5 b_0_1 b_0_2 b_1_2 b_1_1 f_0_8 f_0_7 f_1_7 f_1_8 b_0_1 b_0_2 b_1_2 b_1_1 f_1_2 f_2_1 f_2_2 f_1_1 b_0_1 b_0_2 b_1_2 b_1_1 f_1_7 f_0_7 f_1_6 f_0_6 b_0_1 b_0_2 b_1_2 b_1_1 f_2_0 f_1_0 f_2_1 f_1_1 b_0_1 b_0_2 b_1_2 b_1_1 f_2_5 f_1_6 f_2_6 f_1_5
9x9 DLX prefiltered (2805 lines)
Here are the first 8 lines of the DLX file after I prefiltered it with dlx-pre:b_0_0 b_0_1 b_0_2 b_0_4 b_0_5 b_0_6 b_0_7 b_0_8 b_1_0 b_1_1 b_1_2 b_1_4 b_1_5 b_1_6 b_1_7 b_1_8 b_2_0 b_2_1 b_2_2 b_2_4 b_2_5 b_2_6 b_2_7 b_2_8 b_3_0 b_3_1 b_3_2 b_3_3 b_3_4 b_3_5 b_4_0 b_4_1 b_4_2 b_4_3 b_4_5 b_4_6 b_4_7 b_4_8 b_5_3 b_5_4 b_5_5 b_5_6 b_5_7 b_5_8 b_6_0 b_6_1 b_6_2 b_6_3 b_6_4 b_6_6 b_6_7 b_6_8 b_7_0 b_7_1 b_7_2 b_7_3 b_7_4 b_7_6 b_7_7 b_7_8 b_8_0 b_8_1 b_8_2 b_8_3 b_8_4 b_8_6 b_8_7 b_8_8 f_0_0 f_0_1 f_0_2 f_0_4 f_0_5 f_0_6 f_0_7 f_0_8 f_1_1 f_1_4 f_1_5 f_1_6 f_1_7 f_1_8 f_2_0 f_2_1 f_2_2 f_2_4 f_2_5 f_2_6 f_2_7 f_2_8 f_3_2 f_3_3 f_3_4 f_3_5 f_3_6 f_3_7 f_3_8 f_4_3 f_4_5 f_5_0 f_5_1 f_5_2 f_5_3 f_5_4 f_5_5 f_5_8 f_6_0 f_6_1 f_6_2 f_6_3 f_6_4 f_6_6 f_6_7 f_6_8 f_7_0 f_7_1 f_7_2 f_7_3 f_7_4 f_7_7 f_8_0 f_8_1 f_8_2 f_8_3 f_8_4 f_8_6 f_8_7 f_8_8 b_0_1 b_0_2 b_1_2 b_1_1 f_0_1 f_0_2 f_1_1 b_0_1 b_0_2 b_1_2 b_1_1 f_0_1 f_0_0 f_1_1 b_0_1 b_0_2 b_1_2 b_1_1 f_0_5 f_1_4 f_0_4 f_1_5 b_0_1 b_0_2 b_1_2 b_1_1 f_0_5 f_1_6 f_0_6 f_1_5 b_0_1 b_0_2 b_1_2 b_1_1 f_0_8 f_0_7 f_1_7 f_1_8 b_0_1 b_0_2 b_1_2 b_1_1 f_1_7 f_0_7 f_1_6 f_0_6 b_0_1 b_0_2 b_1_2 b_1_1 f_2_5 f_1_6 f_2_6 f_1_5