The legs (thighs) take longest to cook. If you're cooking just a crown, or a saddle, or just one breast, then it ought to take a lot less long, which should help avoid dryness. (Another thing in that Worrall Thompson recipe that I linked is cooking much hotter, for a much shorter time, than "classical" Mrs Beeton-style turkey roasting -- which also helps avoid dryness.)

This is of course the definitive Empeg turkey thread.

Peter