I've attached an image of a connection I've used (two end plates, reference beams) it seems to work how I want it to but the bolts will go all the through bolt holes.
the plate that is welded to the HSS Tubing I would like to see a tapped hole option (for the plate) so the bolt goes through the first plate with holes and is tapped (self screw) into the plate welded to the HSS Tubing. I think this would be a great connection for dealing with HSS Tubing because unlike W beams and channels you can't really have the bolt go completely through the tube but having a plate welded to the tubing and it having tapped holes is a better solution.
Thanks
Tim Muir