Hey Geoffrey,
Perhaps our elements are a little different in style. I bolted the flange to the outside of the tank sandwiching both rubber seals on the outside as well. So, from the wall of the tank out, it is round gasket, then flat gasket, then metal flange. I did not use silicone on the bolts, but in retrospect I could have. I have not had any leaks so far. As for the nuts, mine did not come with either bolts or nuts. I believe I chose stainless steel for rust reasons. Would love to see some pics of yours when complete. I hope someone will keep making improvements on this model as time goes on.
Of course, the real key to this machine is the electronic temperature controller. Precise scald temps/time yield a precise pluck.