I finally found out why there was a rusty metal plate under each leg
of the T-top in my boat. Two weeks ago, I dismounted the T-top from my
boat and took a good look on the deck where the metal plate covered.
That area was in a bad shape. The fiberglass skin was loose, the
mounting holes were too large for the bolt (like someone tried to
drill the same holes multiple times in various angles), and the core
was totally rotten like wet mud. Obviously, if the leg of the T-top
tried to bolt directly onto this mess, the leg would simply sunk
inside the deck. Seem like the metal plate was meant to spread the
load of the leg to the deck area surrounding the rotten area. But I
don't think those metal plate did a good job. The reason is that the
surrounding area was also rotten and was not that much better.
Actually, the metal plate itself was kind of bending down from the
load of the T-top.

When I removed rotten core from the area where the leg was attached on
the deck, I didn't feel any hard object. Seem like when someone
initially installed the T-top onto the boat, he probably simply bolted
it down on the deck right through the core without using anything like
epoxy to strengthen the holes. Over time, water found its way through
the holes into the core and ended up rotting the whole deck.

This also explains the reason why there are many hair line cracks on
the area where the T-top is attached onto the surface of the console.
If the legs of the T-top was not supporting that well, the load would
shift to other attachment points - in this case, the other attachment
points are on the console. Unfortunately, the attachment points on the
console are not meant to shoulder additional load from the T-top, and
that's how the hair line cracks formed. Actually, this makes me
feeling better because this means there is nothing wrong with
attaching the T-top onto the console as long as the legs of the T-top
is properly attached on the deck. This means when I finish fixing the
deck, I will fix both problems.

Post this just in case someone is interested to know the end of the
story.

Jay Chan