Tom,

If you look up the shear (side load) strength of bolts you'll find it is incredible, so as Phill says hulls simply "hanging" by bolts is no problem.

The uni-strut product is used for mechanical and electrical support in construction, and is available at the next step up from the Home Depots of building supplies. I also found that a trolley/car is available (P2570) for the 1 5/8" stuff. It's rated for 100 pounds but meant to be used in the inverted mode and for it's limited use (movement) in this application should last for years.

Had planned on using this Aussie beam support on my old Hobie trailers (patiently waiting for used/affordable T4.9/F16/?) and may have some concern with hull weights in 30 to 35 kg range, but seriously doubt it, and/or I'm going to find out.