The IRO rims aren't going to weigh much more than Kinlin XR30s, although they aren't as deep and will necessitate new spokes. But if you are going to go that far, you might as well just built up a whole new wheelset that is built just for you, with lighter hubs, strongly butted spokes, a light rim, and lower spoke counts. Track wheels have no dish and are therefore very strong in comparison to heavily dished road wheels. The standard fixie wheelset built with 32 straight gauge spokes, heavy deep rims, and heavy high-flange hubs, is way beyond overkill for most people. If built correctly anyone under 200 lbs can easily be riding around on much less.