I found this thread doing a search to see how others handled this issue and thought a plausible solution was worth posting. I just completed adding Carrera Tensioners to my 2.4L engine...
To button things up nicely on the LHS chain cover, I purchased two longer M6 studs from McMaster-Carr (p/n 98867A265). They are 47.5mm long overall, with a 6.25mm long thread and a 18mm long thread. I was hesitant about the 6.25mm thread being so short, but since it was 1d, I figured it should take the torque (72 in-lbs) without stripping out of the chain housing. Here are the studs:
I used red loctite on the 6.25mm end and threaded them all the way into the chain housing, then used a large OD steel washer with the regular 6mm sealing rings and lock nuts. Looks pretty sanitary to me...
I guess the real proof of this method would come down the road when it is time to pull the chain covers again for some reason... just have to see if the loctite holds when you back off the nuts. I am hoping to not pull these covers for quite some time!
Hope this helps someone out.
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-Doug
1968 911R Clone; 11/07-?? (forever the project car

)
1978 911SC Midnight Blue Metallic Coupe; 7/05-11/09 (so long impact bumpers)
1973.5 911T Sepia Brown Coupe; 9/98-8/99 (went to a great home)
1973.5 911T Gulf Orange Targa; 5/97-11/02 (went back to Germany)