Hi,
If you project will see temperature differences I would steer you away from any material that hardens. Thermal expansion differences could / will stress the solder joints and cause the circuit to fail. This is especially true for SMD parts.
I think you should revisit the silicone. GE Silicone II is neutral cure (according to GE) and will be plenty strong. Some aquariums are held together solely by silicone. And I think you can likely remove it by cutting the silicone around the board.