I've done several (probably 20, though most were crawl space, only a few slabs). Sealing cracks/edges on the slab makes a surprisingly large difference. Use something like OSI quad or sikaflex (those also work great to seal the pipe in the sump hole).
I've used mostly Fantech fans, 4" (and a few 6"). They are very similar to that Eagle. Larger gives you more margin, if you have carpet or other flooring over the slab and can't get to all the cracks.
Use Fernco or simillar rubber couplers to attach the fan to the pipe, it cuts down on noise to eliminate the hard connection.
There's nothing magical about getting to the 4.0 pCi/dL number from a risk standpoint, my understanding is that 10 years spent in a 4.0 environment has the same risk profile as 1 year in a 40.0 environment and the following 9 in 0.0 (it's not an acute toxin like CO), but there often is something about that 4.0 level if you ever go to sell the home. It's a fairly standard target, and a buyer might ask to have levels reduced to that level. They might also be more of a stickler about the guidelines for 10' distance between exhaust and an operable window.
@Legend you are right. Not rocket science at all. I test with a continuous radon monitor, and you can see on the graph when the fan gets turned on. It's pretty forgiving, if you run the fan and levels aren't quite where you want them, just buy another tube or two of polyurethane sealant and a smoke bottle (wind checker works great) and go find where you're pulling air from the top side of the slab.
Good luck, and feel free to PM or tag me here if you have any specific questions.
