Yes, space is an issue, but I have to disagree with the system not warming your pool early in the year.
We were swimming in mid May last year - Ontario - Canada - temps were 85+, and this with only 1/3 of the panels we should have.
I started up my pool in early to mid april, put it on a timer to take advantage of the daylight hours to collect my heat, did not run it at night since you will remove the heat you gained faster.
Sunlight that hits the panels will convert to heat energy, whether the sun is low on the horizon or not, yes, it's not as efficient as mid summer, but you still get heat, and judging from what my system provided last spring, it's plenty, as long as you put your solar cover on at night to avoid losing the heat you gained during the day - if you forget the solar cover 1 night, you're probably looking at 3 days to recover what you lost.
Same goes for the fall time, all in all we gained at least 4 weeks of COMFORTABLE swimming.