Well, I fished up two new lvl1 trammel maps this morning, just so I could see how the pin placement worked out.
I believe the chest location is static relative to the pin, just as we have discussed above. That said, the problem still lies in interpreting the pin location against the either the radar or UO Cartographer.
The first map was in an swamp area away from any of the old locations. I was able to hit that one within a tile or two first try with my 100 mining.
The second map was again in an open area near a mountain in the area created by the new volcano on Fire Island. This one took me about 4 tries to get within 4 tiles and raise the chest.
So all and all I'd say you can get by without mining if you are good at interpreting the maps and have the patience to do some poke and hope. But mining is proving helpful in reducing the search time.