I haven't noticed any apparent weakness from cutting through the hinge line.
That is my yellow plane on his website (121" span 42#'s) and I bent my wingtube bad enough that I almost couldn't get it out of the plane, so it has been put through its paces.

You have to remember where the wingtube ends on your plane and I would recommend not putting one right at the end of it, but inside the wingtube the wingtube will take the load and the closer you get to the wingtip, there will be significantly less leverage.

I haven't lost any sleep over it

John