I'm going to go with "B," it should be fine. I have a switch on a 3% grade (HO, code 83 Walthers #8) and although that's a considerably more gradual turnout than your #5, you should be ok. As mentioned above, watch out for elevation changes or curves close by, but it sounds like you've got that accounted for already. But even in my case, I've got a curve immediately preceding the switch and it still runs smoothly.
One other very minor consideration is that adding the change in direction (i.e. the diverging leg of the switch) on a grade will increase the power required to pull a train up that hill, similar to a curvy uphill climb vs. a straight climb. I've noticed this in my layout in that some heavy trains going up can take the straight leg of the turnout just fine, but will stall on the diverging leg due to that slight additional resistance from the curve.