Chickenlips
Thanks for the advice on phraseology. Unfortunately I am not sure how much good a visit would do as it is usually area control centres that I am dealing with, and often not my nearest centre.
I realise that my aircraft is unusually sensitive to this issue, and controllers are unlikely to know that (it is a rare type). However it is somewhat of an issue with all light piston twins. I do try and inform controllers of this!
G-SPOTs Lost
Not too far out with the 421. However I was taught (by a very experienced 421 pilot, as it happens) to keep cruise power in the descent to avoid engine damage. Ideally I will use 500 fpm for the descent, being unpressurised, giving 180 - 190 KIAS. If descent rate gets too high then speed comes up, and when I do power back I was taught to start the process at a reasonable IAS, preferably level at 3000 feet or below. So far it seems to work, with few engine problems.
High rates of descent close to terrain are unwise in IMC, but single-crew with no altitude select on the autopilot high rates of descent in a busy time of flight are best avoided if possible even well above MSA.