I've got a project that uses a Mega 2560, a SD card and a basic 16*2 LCD screen like this one....https://www.sparkfun.com/products/255 . The components are all glued together using a custom shield I made myself. Everything works fine, but the mega 2560 is more than I need for the project, and it's physically too big for what I want.
I'm thinking of downgrading to an arduino mini pro. Comparing the specs for the two devices seems to suggest the mini pro has all the stuff I need (in terms of I/O pins and SPI technology for the SD card). The coding for the project is minimal (it's a simple voltage and current logger for monitoring battery usage). Does the downgrade I'm suggesting sound plausible?