No. You can only have 64 mixable inputs per iDR, excluding internal FX returns and talkback. The mix engine in the iDR only supports that much. For example if you use four inputs on the surface, you can only use 60 on an iDR64 at the same time. If you want more than 64 channels mixed, you need the dual rack setup, which isn't supported by the iPad MixApp as said. The MixApp doesn't even support the xDR16 channel extension (can't set the preamps). Both these issues could probably be fixed by the A&H programmers with some work... but I'm probably expecting too much support for an app for only about 100 bucks.