Grooved Shubb (or grooved metal Dunlop if you don't want to mess up your decent Shubb). Don't forget to get the fatter strings differently intoned at the saddle too. If you want to be really anal you could do a mini-Buzz-Feiten at the nut too but I haven't tried that yet.

And, of course - be VERY careful about putting the capo so that the front edge is really just ON the fret and don't over-tighten (which is where Kysers fail).

I did try a Bird for a bit and it was crap and soon broke.