Tony
"The question whether or not display pilots get enough practise is relevant only when the display demands skills not normally exercised by the individual."
Surely any display in a 1940s heavy, high-powered piston fighter demands different (just different, not superior) skills to those normally exercised by any current, serving military pilot?
Surely no wise professional pilot should want to undertake a display in an aircraft with which he was not completely and intimately familiar? How many hours of conversion and working down a display to display height is required to gain this level of familiarity?
Even a very benign display consisting of little more than flybys and wingovers is being flown at airshow height, and should not be flown by someone who is not thoroughly familiar with the aircraft, its limits, and its handling characteristics.
I'd have thought that to display a wartime fighter type of aircraft safely, a pilot should have a thorough grounding in a heavy piston trainer (a Harvard or a Provost, say) of perhaps 20 hours GH and aeros, with a further 12 hours GH (not transit) on type before working a display down to airshow altitude. That might seem over-cautious, but I don't think that less than six hours, including transit flying, is nearly enough.