Alien civilizations on large heavy planets may never leave their host planet and develop space travel for this reason. One of the great filters. A planet has to be just the right mass to make space flight feasible. 50% bigger also means they'd expend 50% more energy just by moving around. They would have to have huge muscles (or the equivalent of muscles) to move around on the planet and would have to expend and eat much more calories just by moving around. My guess is that aliens on a giant heavy planet would be massively large creatures. Much bigger than humans. It's just a matter of physics. Probably similar to the large aliens in the movie Avatar.