This whole project actually started by wanting to measure the vacuum inside a bottle without any bulkhead penetrations.  It needed to fit through an opening smaller than most dev and breakout boards, so I was looking to combine a Atmega328 and a sensor on a narrow PCB.  Creating square circuit boards is just a diversion for now.

There are a number of pressure sensors with good Arduino libraries.  To date, I've worked with the MPL3115A and the MS5803, which are at the high end of price and capability.   Here is a little survey I did.

The MS5637 or LPS25HB look like better choices for price and performance.  I also need to investigate the difference in speed between I2C and SPI.  For rocket telemetry, we want to focus very intently on a very brief duration event and that might be a factor. I'm sure that will play in to the EEPROM verses SD card choice as well.