Trevor, I don't think I would use gauze with holes that large.
Trev.
I should do some tests to see what will actually pass through the scavenge pump.
However I did have a few aftermarket sumps on hand and measured the mesh size.
The originals are up in the yard in the top paddock and that is 1/2 mile away but the next time I go there I suppose I should drag out a couple to measure them if for no other reason that to have the size on hand.
Now if you are going to fit an alloy sump then do by all means fit longer studs, much better than allen screws.
Torque should be in the order of 10'/lbs.
Also , very important, fit it with the drain plug to either side, not the front or back.
The reason for this is that should the plug drop out ( usually because you forgot to tighten it fully) then the contents of the oil tank will be blown directly onto the ground immediatly in front of the contact patch of the rear tyre ( not good )