Well, the answer to "how much meat do you get left with if you have a 10.5kg raw weight turkey to share between four people?" is 4Kg, I'm sure you will find that useful.
I couldn't leave the subject without giving a big-up to
S J Fredricks - it was, without doubt, far and away the very best turkey any present (yeah, ok, ALL 4) have eaten. Juicy and flavour like no other, and a skin to die for. Part of that is the cooking advice, for sure, which I followed and required only 3.5 hours, not the 6 hours of yore. No wrapping, no bacon, no butter. Let it rest without covering. Absolutely bloody perfect.