The TPD you are referring to is for 4/8 ohm systems. Of special note: the clamping voltage is 100VRMS.

You need to call TPD and check if that module will work on a 70v system. The audio signal rides on that 70v line so peak voltage can be well above 100v in use.

I'm willing to bet that TPD module can NOT be used on a 70v system. When you go to crank up the system, the TPD module will shunt, sending the amp into protect mode.

But again, call and check - if it can't, they may have a part number they sell that does do what you need.