I have a long (~60') in-ground pool that is relatively narrow, approx. 25,000 gallons, and I'm looking for a robotic cleaner. Many of the models (e.g. Dolphin) say they are good for up to 50' pools. Where should I look for a robotic cleaner that will scrub my longish pool? Is it simply the cord length that limits the pool size, or are there other issues?