Here is the join between the two bits of the tank – it’s taken quite a bit of time and bog to get this right, as well as using a flap disk on a drill to get the radius right. lots of polishing and filling as well. I managed to get some of the profiles right by taking a plastic bog-spreader and cutting a radiuses edge into it. I also found that a wooden tongue depressor also had a very useful profile for putting curves into things.