Also does anyone have any experience with these kayaks, or have any other recommendations?
I chose the Wilderness Systems Ride 115, but as jjbagoose stated, I probably would have been happy with a Jackson as well. You are more than welcome to test out my kayak this spring - just let me know (I'm a few towns over from you and easy access to the Charles).
I used the foam blocks for a few months before getting a roof rack. The blocks will work, it can just get a little shakey on the highway. Don't forget to strap it down FRONT & BACK as well as over the top(just ask me how I know.....) and you should be fine.