: When you have two yaks on their side do you need some sort of vertical post
: on the racks to act as a support to stop them tipping or can you rig it so
: that the boats support each other?

I have found that two yaks support each other well. I cross anchor the front of the boats to the bumper and put one strap around both boats in the middle making them behave more like one unit. Putting the first one up in the wind can be a trick. It is easier with hard chine boats. I have a firm pad underneath them to protect the chine stress points but not allow very much wiggle. Someday I may invest in saddles but I consider them a nice to have not a need. Having said that I own 11 boats and store them all on a trailer that has J brackets for the yaks. I will often just hook onto the trailer for convenience even if I am only using one or two of the boats that day. If you get the building bug you may want to break down and buy a trailer they work well for storage and transport.