Goss is a Prestolite type brand of air/acetylene torch.
Beverly, a 2" x 2" sheet isn't that big unless it's a thick gauge. If
it's 20 gauge or so, then yes, it can suck up some heat. Either way,
Kelley's suggestion of a binding wire nest or something that helps
get the sheet slightly up off the soldering block will help. The two
biggest mistakes I see when people are soldering something small to
something larger is that they either don't give the piece enough heat
(moving too slowly, flame too small, or brick sucking the heat away)
or they have a big enough flame, but in an effort to stay away from
the smaller more vulnerable part like a bezel, they move the torch
around too far outside the edge of the sheet, which means the sheet
isn't receiving all the heat. That's an easy mistake to make when
keeping the torch moving quickly.
You're right to use easy silver solder on the bezel since you're
soldering it to the silver side of the bi-metal. It will give you
better flow than the 18k solder.
Hope this helps!