Sorry, as a goo enthusiast I assume everyone knows these terms.....

Room Temperature Vulcanizing .... Silicone ,,, and I would use the red gasket heat resistant type... GE is one brand but don't know any bad ones...Devcon,locktite,

In other words... the heat resistant stuff used for sealing gaskets to metal... they have lots of body... but if you need to span an open space you can just use something like brass sheet ( shim stock) and place it on the outside to get initial support to the gob of RTV.....

All regular auto parts stores have it , but may can get it at any hardware store.

cleanliness is the key... and leaving it with no load 24 hours at least to cure to final strength...