VPPro shoes - I have some myself, the wear is good, and they're inexpensive BUT beware, they are designed for 26.5mm internal clutches... not the smaller ones like the Mugen's (26.1mm). They "work" with the mugen clutch but engage a tad too early.
Tony's S5 rings are the best cure to leaky diffs indeed, but the diffs shouldn't be topped off any further than the satellite gear axle anyway, even with Tony's magic o-rings
rebuild and grease the diff outdrives well too
Paul