Changing size limit on MQTT packets- Photon


I am trying to increase the default size limit on MQTT packets from 255 using the standard Niaasto MQTT library available thru the Web Particle Builder to something like 512. My apologies for the simple question, but I grabbed a copy of the MQTT.h, renamed it X.h and included it with my code using the + command in the web builder. I did nothing with the .cpp, but in my code I include “X.h” Everything compiles as seems to run as normal. However, as far as I could tell the size limit was not increased. What have I done wrong or is there a limitation somewhere else?