Re: Swing weight question ?
Silver Creek has offered some sound advice here. He is describing the mechanics of rotating masses. When you think about the motion of casting, it is largely a rotation about some pivot point (your hand).
You can think of the rod as a beam with a tapered mass distribution and the reel as a counterweight. Every rod/reel combo has a balance point, the center of mass. Ideally, you want that point to be somewhere near the grip so that the rod comfortably rotates about your hand (it depends on your casting stroke, but I prefer a balance about my 1st and 2nd finger). If the rod has too heavy a reel, the balance point will be too "low", a light reel vice versa.
Balance and swing weight are different. However, both are important to comfortably casting all day. If the rod is not balanced, your hand/wrist/arm muscles must compensate by torquing the rod to rotate. Swing weight has more to do with how much mass is located away from the balance point (center of mass). This property is called the "moment of inertia" in physics/mechanics.
Think of a barbell. It has a center of mass in the middle of the handle (where you grab it). A barbell is very difficult to "twist" because of there is a lot of mass away from the center of mass. The further the mass distribution away from the center of mass, the worse (much worse actually) this problem becomes. The whole time you are trying to rotate ('twist') the barbell, it is balanced about your hand.
Now think of your rod. You want it to be balanced so that it comfortably rotates about your hand. You also want it acceptably light so that the swing weight (moment of inertia) is not too tiring after hours of casting. You'll here the terms tip heavy or tip light. Sometimes these are used to describe the mass distribution, sometimes these are used in an inconsistent manner and can lead to confusion.
Perfect example: I have two 2wt rods. Both are exactly the same weight and length. However, one rod is lighter in the tip and heavier in the butt. This rod requires a lighter reel to balance. The rod/reel is therefore lighter in general. Because of this, the rod has a lower moment of inertia and a much lower swing weight. It is vastly easier and more comfortable to cast.
The heavier tip rod needs a (slightly) more massive reel to balance properly. However, if I simply added an even heavier reel to make the tip feel lighter, all I've really done is shifted the balance of the rod lower (toward the reel). But inherently, I've worsened the situation. Now the tip mass is even further from the balance point which is now uncomfortably low. And the more massive reel is acting as a more massive counterbalance and is also causing me to apply more torque to the system, and that torque is not being applied about the center of mass because I'm not gripping the balance point. I'm turning the system into a barbell...a barbell that I'm not gripping in the middle.
In short, a more massive reel doesn't help. The mass distribution (think taper) of the rod will ultimately determine it's swing weight. You should balance the rod with the lightest reel that will put the center of mass in the comfort of your casting hand. Longer rods will inherently have higher moments of inertia and require more massive reels to balance. That's why it's important to get a light tipped long rod for comfortable casting.
Hope my thoughts help.