Don't take offence at this... but have you seen what a PCI and an ISA card look like? If you recall, they look very different because with the rear panel at the back the components are either right sided on an ISA card and left sided on a PCI card.
Another hint. Those shared PCI/ISA slots on a standard motherboard? The slot (actually the rear bracket cutout) will take either a PCI card (and screws up the use of the ISA card in the next connection point), or an ISA card and no PCI.
Now, the WSP has two connectors (ISA up top and PCI down below) that is the same as a shared slot on a regular motherboard.
If you are careful and remove the bracket from the ISA card (and maybe a few rear panel connectors too) then you can mount the PCI card in its slot and screw its bracket in, and then also fit the *modified bracketless* ISA card into its slot, being very careful not to short components between cards.
Using electrical tape over the ISA card (or the PCI card) is probably a good idea.