@Curryhouse in theory anything you do to the a frame can potentially weaken it. if you look at the mark a u bolt leaves on the corners of the tube after install that has the oppertunity to become what is referred to as a "stress raiser point " and for an example would be a "no go" in aircraft or racecars. follow proper guidelines and common practices and you will be fine. There will be a lot "redundancy " built into the engineering of a Jayco drawbar. After all how many Jayco drawbars have we heard of failing?
Don't weld across or ideally screw anything to the topside of the drawbar tube. The sides are fine for screwing, and welding but you still want somebody that can weld properely. screws ideally keep to the centre of the tube. Additionally you have issues with wires needing to be removed from the drawbar beforehand if welding, which can be a pain.
As
@Soaring said u bolts are ideal in many cirmstances on the drawbar.
Below is how I did my gas bottle relocation with u bolts, but also welded on the inner jockey wheel clamp. But you'll notice I bent the upper support to cross the drawbar tube and only welded it on the opposite corners not across.
The ubolts are solid as and offer no deflection.