Hi Tim,
As a person that has had a large preformed pond and now has a flexible liner
pond, I can tell you that you would be better off going with a flexible liner.
You didn't say where you live, but if you live any where there is cold weather
and freezing temps, the ground can heave as it freezes and push the preformed
liner so that it is not level anymore. We had a 270 gallon preformed pond.
And believe me, my hubby had it as level as it could get. This spring we
noticed that it had really sunk on one side. We live in Idaho, and have snow
and freezing temps most of the winter. This happened within a 2 year period.
My hubby figured it was sinking some each year but we just didn't notice it
until this spring. Hope this helps you.
Jan
"Our Pond" Page
http://hometown.aol.com/pinkpggy/index.html