Augaug, do you think that mako supports 30" apart with fore and aft straps would be ok?
I think that anytime you're dealing with bars that are 30 inches apart, you've got a less then ideal circumstance. However, I do think that the Mako saddles, and a bow and stern line fitted relatively loosely works quite well.
I have pictures and a more detailed description in this post here:http://www.hobiecat.com/community/viewtopic.php?f=71&t=28959&hilit=ai+review
If you look near the bottom of that post, I talk about how I transport the boat. The picture shows the ama's on top of the boat, and the sail below (and between the saddles) That set up just allows me to take our second boat on the roof. If I'm travelling with just the AI, then I put the Ama's on either side of the boat to lower the centre of gravity and increase aerodynamics.
Let me know if you have any other questions. I do want to say that not everybody feels that my system is perfect, and they're right. But given the 30 inch separation, I have yet to find a better solution. Long term, I plan on building a custom trailer to take two boats, two bikes, and camping gear.