With 128Mb of fast ram you're going to be in a position where its more likely you'll run out of chipram before reaching the limits on the fast. Even with the Spectrum onboard you're gong to struggle to use it all. Also given the costs involved, even if it were possible to add more via the Z2 slots, that is a slot you have essentially wasted. Get a USB or a eithernet board before you start thinking about doing things "because I can".
