I think we're running into a language and translation issue when it comes to "weight" and "encumbrance". Or maybe it's just that both factors are so interrelated that it's hard to draw a line between them. So to try to clarify what I mean, I'll explain how I use the terms "weight" and "encumbrance" when it comes to clothing/armor. My meanings for these words are probably different from what Madoc and most other people use, but by making these differences obvious maybe we can all communicate better. So....
To me, "encumbrance" means losing range of motion in your joints, losing fine control of movements, losing tactile feedback. IOW, it's a control issue. You can still move easily within the range limits imposed by the encumbrance, but you're clumsy and you have limited range of motion. Depending on what you're wearing, you can be heavily encumbered despite your gear being very low-weight. For example, heavy gloves (or, worse, mittens) don't weigh enough to matter and still let you wiggle your fingers at high speed, but destroy most of your manual dexterity through entombing your fingers in thick padding.
OTOH, to me, weight (or, more correctly, mass), as long as it's within your strength to move/carry relatively easily, has most of its effect on the acceleration and maximum velocity of your motions. If it's really too heavy to move/carry easily, then it largely restricts and might even prevent movement at all. The more massive something is, the harder you have to work to overcome its inertia to get it moving at all, and the harder you then have to work to stop it or change its direction of motion. Therefore, for a person with a given amount of strength, a heavier weapon would have more delay between clicking to attack and the attack starting, and would also move slower than a lighter weapon used by the same person. The slower top speed is due to knowing you have to stop the thing and recover to a guard position, and you don't want to get it going faster than you can easily stop quickly. Same with wearing armor; heavier armor means slower reactions to start moving in any direction and then a lower top speed so you can stop and/or maneuver in a timely manner.
So, as I use the terms, mass can neither be created nor destroyed, so you're stuck with that and the only way to deal with it is to have higher strength. This is determined at character creation and subsequent time in the gym. But encumbrance is more of a comfort thing. It has an irreducible minimum due to the bulkiness and inflexibility of your gear independent of its weight, but that minimum can only be obtained by properly wearing the gear. If you know how to adjust the straps or whatever, you can mange to be less encumbered than somebody else in the same gear who lacks that knowledge. This is where skill would come in.
So, consider a person in plate armor. The armor is designed to offer essentially the full range of motion with minimal resistance to movement, but that only happens if you're wearing it correctly (and it's sized to fit you). If you lack armor skill, you'd have less range of motion, less precise control over your attacks and parries, etc. And the weaker you are, the slower you move/attack/parry regardless of whether you have armor skill or not.
Sony Vegas skills to show proof. 
