I wish I had consulted this thread prior to me designing my bike rack for the front of our expanda. A lot of good ideas here. I have a 4 bike rack on the back bumper. I cut a 75mm square hole through the guts of the RHS bar with an angle grinder. I then welded heavy wall RHS through the bumper to accept the 50mm square hitch bike mount. On the front I made a custom mount that accepts a 50mm tongue hitch and ball. I then mount a standard 3 bike ball mount bike rack to it. I did it this way so I can quickly and easily remove the rack to access the spare tire. The mount utilizes high tensile draw bolts and a clamping plate. I did not weld directly to the A frame as I believe in keeping things as standard and as "pretty" as possible. I have noticed that some people have welded RHS directly to their A frame. This is a no-no in the trailer manufacturing world. Welds should never be applied "across" the RHS A frames as it presents a stress point and can result in metal fatigue and failure. If they are required, they should be done in stitches with equal gap to weld spacings. The welds should if possible be done "along" the A frame from front to back or vice-versa. ( check out your trailers and caravans, they should not be welded across the RHS. ) I will try and get some photos to post up here. Maybe my ideas may help others (Maybe not).