Well I have been kicking this over for some time now and ready to pose the question here.
I see many people using the silicone seals on their stills, yet when I search for advice on using silicone it's a "no no". If I use a pre made seal of 100% silicone then why can't I make my own from the same material in the tube form. I have found many "food grade" commercial sealants in the liquid form for use in the food equipment industry. A lot of these RTF Silicones (100%) are widely used in the food industry and are recommended for food contact and temperature rated. I have also looked at "many" aquarium sealants and they are the same composition as the food sealants.
So why the taboo on the DIY silicone seals? just Wiki look up copper and see how toxic it can be to the human body.
The reason for this is that my current build has sight glasses that are non standard to the seals sold on the distilling sites. Everything has it's warnings on this planet and the mere fact that alcohol is a toxin to the body I don't see how the silicone can be an issue, especially when your making seals from the same material that the seal manufactures are making them out of and selling them for this very application.
Having said all this I certainly would not use the same silicone used to hold the oil pan on my car.