There's not much space under the false bilge. Maybe 1"-2". You should be able to tell if its been done by looking at the sides where it was cut. If it was done the there will certainly be some signs. Also, the actual bottom of the boat is not as smooth as the liner. Think lumpy, uneven fiberglass. Unless painted there is a color difference too.
I used a hole saw at first and tried to drain out the stagnant water. It worked fine although it was not a complete solution. There was still the stinky rotten plywood underneath and the only way to properly due this modification is to Do it correctly. You may want to try the holesaw and build up your confidence first. I also seen that some owners remove as much as they can hole saw and trim it up afterwards with a Dremmel tool. Once you drill through the false bilge and the plywood with a whole saw the core should come right out. You can look at the core to determine how it is constructed and how much space there is. Keep in mind that the space may not be consistent from one end to the other.
I used a hole saw at first and tried to drain out the stagnant water. It worked fine although it was not a complete solution. There was still the stinky rotten plywood underneath and the only way to properly due this modification is to Do it correctly. You may want to try the holesaw and build up your confidence first. I also seen that some owners remove as much as they can hole saw and trim it up afterwards with a Dremmel tool. Once you drill through the false bilge and the plywood with a whole saw the core should come right out. You can look at the core to determine how it is constructed and how much space there is. Keep in mind that the space may not be consistent from one end to the other.
