A radio frequency (RF) transistor amplifier package includes a submount, and first and second leads extending from a first side of the submount. The first and second leads are configured to provide RF signal connections to one or more transistor dies on a surface of the submount. At least one rivet is attached to the surface of the submount between the first and second leads on the first side. One or more corners of the first side of the submount may be free of rivets. Related devices and associated RF leads and non-RF leads are also discussed.