I have only made one rye beer - about 25% rye malt. It was very viscous (in a good way). Its my understanding that this mouthfeel is inherent with rye malt. So, although lower mash temps, eliminating cara-pils (definitely this one) and adding adjunct sugar (and less 2-row) would decrease mouthfeel, these things will essentially be trying to compensate for mouthfeel that you will get from the rye. But its worth a shot.