Ripple-fire probably pushes the ship sideways more than a full broadside would, given that, in spreading the recoil over a longer period of time, it provides a more sustained push. And American BBs in general (and the Iowas in particular) always had heeling problems, due to the fact that the beam was dictated not by the needs of the gun platform but by the width of the Panama Canal. Compared to other BBs of the time, Iowa et al. were skinny.
Never heard of the firing limitation in GWI Act I...and I don't doubt it, thanks for the info. It must flex the keel something fierce, with all that recoil along the length of the ship. It yet again illustrates my point that, despite mounting big-ass guns, the BBs themselves have limitations that make them poor gunfire support platforms.