KC-130Vali clamp is pretty strong but in a good way - you don't feel the weight at all and the headband is very soft leather anyway. Would compare the clamp feel to fresh HD600s only with pads that are not very soft. The real reason you feel it is because the ear cushion foam is very firm for acoustic reasons and a lot of headphones out there are now shipping with memory foam stock, its simply relative.
You will definitely need to adjust them for your head at first using the screw adjustments at the sides but once you have it perfect they won't budge, so after that it's very easy to simply wear them for hours without any issues.