Recently I've changed the rocker cover gaskets but there remains a slight leak.

I did everything as per the instructions here.

I used degreaser and cleaned the covers well.
Inserted the gaskets, turned upside down and no part of the gasket fell down.
I used a torque wrench set at 3.5nm

How tight should the two metal layers be on the rocker cover once the gasket is inserted in there?
I assume I can just reuse my gaskets rather than buy new ones?

I had a similar issue. Started leaking again after a week or so, retensioned the bolts and the problem hasn't resurfaced.

To 3.5nm again?

To 3.5nm again?

Until it was tight, but not overtight or pushing the gaskets out the sides or anything like that.

did you re size the tin with pliers before installing the new gaskets ?

Yes I did.
Though I am not sure if I did it correctly.
The gasket would not fall out if I turned the cover upside down, but it was not in their tight either. I wasn't sure whether I had to resize it such that the gasket was snug in there?

On my old 74 I had the same problem, it's not recommend to use any sealant but I used a very thin layer of ultra black and they never leaked after that

I had a slight leak a year after changing mine when I changed to sythetic oil. A little bit tighter where the leak was fixed it up.

I assume I can just reuse my gaskets rather than buy new ones?

I thought you would always use new gaskets???? The reason they leak is that they go hard over time and don't seal properly. I bought a gasket for about $22 at Repco, so not a large expense.

he just put new gaskets on and still has a leak. yes you can reuse the new gaskets try retightening the bolts first. then if there is still a leak check the fitment to the cover and re adjust the tin.

pretty common problem if not fixed but oil can seap into starter motor after awhile can cause a dead short when starting causing the computer to reset

Yes I ended up tightening the bolts by half a turn each and the leaking stopped.
Actually I set my torque wrench to 2nm rather than 3.5nm initially as I was concerned about accuracy, thinking I can always tighten if need be but if I warped the rocker covers it'd be a huge headache.