If you are using the dimarzio screw, then keep the brass bit on, but if you want the strapbutton then use the screw that came with the guitar and remove the brass bit.
To remove the brass bit, simply wedge a screwdriver between it and the material and then lever it out. It's really really easy.
The material of the strap is polyester(i think)? In any case, the fabric has already been melted round the hole to form a solid circle of plastic around the hole so that the brass bit doesn't tear it, so putting a screw through it will be fine.
The reason I would actually recomend using the original screw +
strap button as well is that not only does it look cooler, but I have had problems with an RG i have where the dimarzio screw just came out all the time. *I tried to fix it with the original screw and then decided to use the strap button as well, no problems since, and now I have done it to all the guitars I have with straplocks.
It'll hold well with either method, and my guitars do get thrown about a bit (well, only when they are hanging of me, the rest of the time I take good care of my children)
