Repeat question about roof studs?

Whatcha.

I think this was asked a long time ago but I can't find it. 

I have roof bars mounted to the existing rail studs they are fine if a little ugly. I seem to remember that some people just dispensed with the rails and then shaved the studs to give a clean roof which is an appealing idea for show days.  However shaved studs is a decidedly permanent solution that prevents refitting bars or rails. To my mind the obvious solution would be to replace the studs with rivnuts then it's both clean without the bars but still practical with them. 

So the actual question.  Before I take my head lining out,  how are the roof studs fixed?  Are they like a wheel stud and splined to locate them in a thicker section of roof seam such that they could be driven out or are they somehow welded or sandwiched between the roof skins or something else that makes cutting and drilling the only option?  Oh and you are right a rivnut will need sealing properly. 

Cheers for that. Hmmm so looking at that picture I would be needing to remove the heads too to retain the spreader plate whilst minimising the section depth to allow the rivnuts to work. OK that's doable. More thinking time required.

I think that it's the usual reason suzuki do anything odd, because they can.