We were really happy in Carlos and Cristina's apartment. It's perfect for 4 as there is a master bedroom as well as a 2 single beds room. A small but well equipped kitchen and a comfortable bathroom. The flat is right where the Ribera (and nightlife) starts and there is a fado house just below if you are lucky to be at Carlos and Cristona's during the fin de semana.
Also is a quick walk away from all the cavas :-)
If we come back to Porto we'll stay here again for sure.
Thank you Carlos and Cristina!!!