I have installed the Bilco one a job and also installed another brand (I can't recall the name) on a different site.
Both seemed like good products. The Bilco I think was better, the "lid" did not appear to be the type to go traveling with the wind.
But I have not been back to see if they are still intact.
I would recommend that you use gravel fill around the entire unit. And you are doing well by making sure you have gotten down to the drain system around the house.
When we set them, we mark the location of two holes then drill and set it with a wedge type anchor. That will hold it in place, then drill and set the rest of your anchors. It is a fairly easy install.