We use stainless steel element terminal bolts.
There is no problem whatsoever venting the kiln out of the roof as long
as you take precautions to protect the opening like you would any roof
An instructional video for assembling an L&L Top-Loading DaVinci kiln
The discs are placed in the element holders to keep the elements from coming out during shipment.
It is not necessary to keep them in place for the first firing.