I forgot to mention, that these original hp reference are a bargain for around 100$. LTZ1000 /A cost 35.. 55$, 3 PWW or MBF for 10..20$ each, plus the additional stuff. They only need a thermal shield around the LTZ1000A on component and solder side, the pimping to 55°C (by 100k PWW in parallel to the 15k BMF), a shielding, and a PSU. The circuit is the same as in the LT datasheet, that's totally sufficient for stability. And it's very compact, easing the shielding. No fancy slots or other gimmicks for the PCN and components.. The stability is determined mainly by the LTZ1000 and its oven temperature. Therefore, that's a recommendation. FRank