The angle of bank requred into a x/wind at or below the demonstrated limit of most aircraft is not excessive. Certainly not enough to slide you out of your seat. I personally crab in then change to wing down for the landing. If I crabbed all the way to the flare and got some float and hence drift, this is what I'd be doing anyway.
As for the avoidance of flap in the slip in a 172. My considered opinion based on considerable experience is.... B...ocks!