The floating problem is solved with this kind of light weight medium by simply moisten it well, prior to run the system. If wet it doesn't float or go anywhere. It doesn't dislodge any roots neither then. The very same is done with perlite, which is even lighter - in case it is used in E&F.
But most systems based on chips or/and sawdust do not use actual E&F, or any recycling system as I said earlier. The sawdust or mix get filled in porous (woven) poly planting bags (of adequate size) first. Then you actually close the bag, turn it or lay it flat, pinch or cut a hole(s) in the bag and transplant your seedling through the slit in the medium. Then you simply drip (often a pin dripper is sticked in the bag) and let go to waste, evaporation actually. Obviously (for the skeptics) cheap
nutrients that are manufactured from raw materials on site are used with this rather "wasteful" technique.
Well, that is the technique that I know of and that is commonly used with sawdust and chips.