resDQ

Now that the forums are heating up again, does anyone have more to say on this?

I contacted POIs at three schools I applied to last year. In one instance, i was accepted with a fellowship nomination, in two instances I was rejected. I suspect contacting POIs had a role in the acceptance and one of the rejections, but not the other. I would say that unless you're emailing them to make sure they're taking advisees, don't contact them.

No need to mention that in your SOP; it will not help, and will likely hurt. It's perfectly fine of a goal to have, but this is not what top schools are interested in. 
As for you, @resDQ, no, faculty at top schools are not interested in having their students at LACs, despite the realities of the job market. They are training you to do research, not to teach. Feel free to mention your goals, will not hurt you. 

161 as a quant score would not get you rejected anywhere.

You're never going to be "locked in" to what you say in your SOP; it is expected that your interests will change. Unless you have an extremely niche interest, even if your interests do change, you will probably still have someone to work with, and if worse comes to worse, you can often have a committee member from another department or school. 

The way to avoid that scenario is not necessarily during the application stage, but when you're making the decision of where to go.
I'm not sure what subfield you are, but the polisci methods sequence should be sufficient unless you are a methodologist who wants to specialize in a specific thing the department doesn't have to offer, in which case you'd take courses in another department or at ICPSR in the summer.
If this part is of vital importance (and it really can be depending on your research interests) then you may want to check out the courses that make up the methods sequence and see if the courses within it satisfy your needs. If not, look up the requirements for earning the PhD and youll see if they allow outside courses to count towards it. This will help you narrow down schools in the selection process.
I don't think there's any reason that requesting to take courses in other departments would be offensive, but I would word it in a different way so you can further sell yourself in terms of fit. You can mention something along the lines of the department's openness to an interdisciplinary methods training if necessary is crucial to you having the specific skill set needed to answer your research questions. Therefore, the quality of your research would increase and the research you do in the department's name would be higher quality too.