the ratio thing means that the shock's stroke length is only a third of the travel. So say a bike with nine inches of travel at the rear axel has a shock with a stroke length of 3 ionches, it has a compression ratio of 3:1. So that doesn't mean a 900lb spring for a 300lb rider.

In actual fact if a bike as described above had a 900lb spring, it means it takes 900lbs of weight to compress the springh, and hence shock 1 inch. So for the shock to bottom out, 2700lb's are needed. This would equate to 300lb's needed to move the rear axel 1 inch.

I used to use a 550lb spring on my bighit and if I wanted I could probably have gotten away with using a heavier spring, even though I am light 55kg I still needed areasonably heavy spring (for my weight) because I did big drops/jumps and I liked the feeling of a hard shock, espescially for racing.