I thought it was fine (totally ridable), but didn't provide the same level of damping change and isloation I feel on some other boards, and it did (slightly) seem to stiffen the center section. I have several boards (SG, JJA, Virus) that are in the 185 GS ballpark, and I enjoy a plate on those more. I think the Contra in good snow is damp enough, and benefits from being able to use your fee to flex the board more that I find necissary on the GS stuff. On any of them you can just tilt and engage the side cut if you want, too, but on the GS stuff I enjoy the feeling of tip/tail weight shifts that the Coiler seems more indifferent too, and the plate leverage just didn't make a big change for me (albeit on softish conditions).
I should note that I mentioned I enjoyed plates on boards in the class (my Contra is a 180 with GS+ type sidecut) and wanted that option. Bruce seemed fine with that, and on his preference we kept it 4x4 rather than add UPM inserts. I find on the boards that preform best with plates, I don't feel a huge difference between UPM or 4x4, so keep the UPM plates on the boards with those inserts. I have another shorter board/ longer side cut on order that I'll also try with a plate, but based on my experience with this one I assume I'll run it bare. Note that I'm riding in CO, and firm conditions here are like powder days in the NE.