As noted by Silvaire1, to reach the operating ceiling one will finally be climbing at something like Vy, which is itself close to Vbg (best glide speed).
I've taken the TB20 to FL200 a few times and there is really only one way to get up there: leaning all the way up in a constant-EGT climb and at the very top watching the IAS very carefully, and at the
very top of the climb the stall warner is intermittently coming on. ISA +/- a few degrees makes a significant difference too.
Takes a good half an hour...
But I don't think the OP was interested in this
