Leak around tank bolt on new toilet

I just installed a new Toto Drake two-piece elongated toilet using the directions provided in a posting on this forum (excellent instructions, by the way). Anyway, there is a consistent seep around the bolt that holds the tank to the bowl on the left side. It drips a few drops per day. I have taken the tank off and lightly sanded the area inside the tank where the gasket for this bolt contacts the tank and reassembled. I tightened both bolts enough to get the three points of contact that Toto specifies, but I don't want to risk tightening so tight that I crack or break something. The seep and drips are still there. Any thoughts how I can stop the leak in this area? Otherwise, I am extremely pleased with the toilet.

Take the tank off.
Tighten the bolts on the tank.
Set tank on bowl.
When you are tightening the tank to the bowl you must use a screw driver in the tank so that the bolt does not spin. They must not spin or move. I have tried this out on three Drake's I installed and found this was the issue for me, mainly because I used a rachet to install them without using a flat head screw driver in the tank.

Hope this helps.