in my opinion there should be no need of adding additional ground, make sure that the connections are clean, no corrosion on any contacts, from tranceiver to tuner to antenna!, and also check the ground connections for contact / corrosion. Also check the dynaplate if it is clean and not painted... Transmitting problems are very often connection problems on the path to the antenna (antenna - tuner connection...)
If you decide to add anything else to your ground system that is connected to the bonding system (and this is the only thing that will make your ground better, or - of course - copper foil) then make sure that you put capacitors between tuner and bonding so that there is no DC connection between your tuners ground and the bonding so that only HF can pass.
Kali Mera has no dynaplate, I use the bonding as HF ground, but separate it with capacitors so that omly HF can pass it, that works fine and does not change the Amel bonding philosophy. Bills idea is also good, but it might be a too small area for effective grounding.