Some of it is done in Oregon, around Medford to Salem, going from 50 degrees through the clouds over the Cascades pretty guarantees upslope icing....if you keep climbing into wet clouds trying to get pushed over some mountains, your gonna get some ice..
The ATR went through flying around with some tanker in front dumping water at them around the freezing level..
Personally If was going to do it, I would find a sub freezing ambient condition with a wind tunnel,cold soak the plane overnight,, blow on it for a half hour to get everything cold and sticky........ get some fire hoses....that should do it....