This page contains a gallery of symmetric forms, that you can make of bridged Triamonds. I would like to find all triangle-mirror symmetric forms with solutions because of my addiction to systematic approaches, but this is maybe later. The following forms are currently only a selection.
9 * 6 solutions
12 * 6 solutions
no solution
7 * 6 solutions
7 * 6 solutions
1147 * 6 solutions
911 * 6 solutions
23 * 6 solutions
61 * 6 solutions
64 * 6 solutions
99 * 6 solutions
204 * 6 solutions
29 * 6 solutions
8 * 6 solutions
5 * 6 solutions
2 * 6 solutions
15 * 6 solutions
11 * 6 solutions
1 * 6 solutions
no solution
4 * 3 solutions
2 * 3 solutions
6 * 3 solutions
40 * 3 solutions
7 * 3 solutions
5 * 3 solutions
3 * 3 solutions
2 * 3 solutions
1662 * 2 solutions
45 * 2 solutions
8 * 2 solutions
169 * 2 solutions
68 * 2 solutions
93 * 2 solutions
31 * 2 solutions
152 * 2 solutions
79 * 2 solutions
67 * 2 solutions
20 * 3 solutions
157 * 2 solutions