Well I WAS 6' , 190lbs a few months ago, but I''ve lost 20 lbs, so I'd say 170 lbs is gettn pretty skinny.
I found I like IWB the most comfy. I carry an XD40SC which is pretty heavy and thick. I get the best support and all around comfort IWB in a Dakota Defender. I find IWB is even more comfortable since I lost the weight than OWB is. I've got a good gun belt, but I can feel the weight of the gun alot more with OWB.