@Eniodis
I've got an A1230 + Mediator PCI. I don't know if it's the same with an A4000 but it works with mine : just download WBCtrl from the Aminet.
Add :
WBCtrl IMT=FAST
in your user-startup and the memory from the Mediator should appear in your Fast RAM. So you should then get 16+32 Mb Fast
That is NOT true.
You will NOT get more fast memory with that, only less.
IMT=FAST will only instruct Workbench to load icons to fast memory.