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.