I AM NOT AN EXPERT!!! please take what i say with the intention that i want to help and learn. that said i have a few questions

why choose silicon? I keep cans of that expanding foam crack insulation on hand. it expands to something like 10 times it size filling all space in a crack. and its fast to apply and dries quick. is there something about silicon that would act as a better sheilding?
where is the toilet vented to?
the water that is used as additional shieding. is this the water your going to drink?
i belong to a few other forums and we basicly descibe our set ups and then let the others find all the holes. so we can fill them <img src="/images/graemlins/grin.gif" alt="" />