How about making the fiber pads thinner (you might be able to sand them) or going to the LHS and finding a thinner pad. If it is necessary you could glue the thinner pad to the metal pad to help keep it in place.
I would also use a fiber pad in between the 2 disks to increase the friction on the disks.

I think the reason PJ quit using the 2 brake plug mod was because he found it impossible to adjust.


rolland