I've never invested in a dedicated synth progression. Normally, I trail off in the 3k-5k range, leaving the rest to naturals. Here, I'm thinking the intended progression might be 1k > 6k or 1k > 3k > 8k, not that I need to try another 1k > 6k combo. Silicon carbide lapping stones are generally poo-pooed, but even this double-sided (120x/320x) "double-time" lapping stone seems interesting. Only thing is, what to use to lap the lapping stone when the time comes.