home built 4x40 RO system upgrade.

Hi I built a single 4x40 membrane RO system with a 240 Procon pump a few years ago and it works great. Now I am looking to improve my system to allow me to run it less hours. I am wondering what you guys would recommend adding a 2nd membrane, adding a re-circulation pump, or larger Procon pump? I am worried if I add a 2nd membrane that it will foul quicker without adding more flow.

To reduce time running the RO a second membrane makes the most sense. Most run 2x 4inch membranes on a 330 procon. What HP is your current motor?

Right now I have a 1/2hp motor running my 240 Procon pump. If I go to a 330gph I will need to bump up my motor size to 1.5-2hp 220. This is not a problem if it my best solution.