PsychFish -
RO membranes are made at different production ratings. This is affected by the size of the membrane and the materials it is made of. I am not familiar with the 25gpd size unit so I would be curious if the membranes are the same size. They probably are, but your filtration unit is only designed to produce 25gpd at a certain water quality level. By attempting to increase the water output, it will mostly likely result in much poorer water quality.