Welcome aboard - I do like the red ones!

Regarding the preload - having it set at 5 (highest preload) won't make the spring any harder (spring rate stays the same), all that it does is increase the rear ride height and reduce the suspension sag (how much the shock compresses under the bike's own weight and, more importantly, when you climb aboard).

Jacking up the rear with the preload will serve to quicken the steering, but the sag will be reduced, and if you're not particularly heavy it will cause the shock to work only in the upper part of its travel (you won't be using its full stroke) and it may top out, which can give a "hard-bouncy" feeling. As a very rough guide when you sit on the bike the shock should use up about a third of its travel.

There are loads of good videos on You Tube showing how to set suspension sag - have a look.

This is a fairly simple guide too: http://www.strappe.com/suspension.html

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