Paul - 11 lb (5kg) from the MAFF chart published by Jane Grigson is around 3hrs 20.
The 3hrs 40 you gave was appropriate to Vernons 6.5kg leg.
So it sounds like the 3hr 20 timing could be spot on for your bone-in leg.
Does anyone actually have MAFF Bulletin No 127 ??
I'll ask if the local library can find a copy...
I alluded to the thermal conductivity of the bone in my commenting about Vernon's experience.
There is a comment in Julia Child's "Mastering the Art of French Cookery" in which she discusses this in relation to roasting legs of lamb and mutton.
A boned leg or shoulder will weigh approximately 30% less than a bone-in piece, but its cooking time per pound usually more than doubles, depending on the thickness of the meat"
I'm also surprised that brine calculations seem to ignore the possibility of a significant part of the total weight being bone...
The time to get the core up to something like 70C will also vary somewhat depending on whether the starting point is 4C (fridge) 15C (dry-cure conditions) or 20C+ (summer or tropical ambient).
As regards the core endpoint temperature, in their "Charcuterie" (at page 62), Ruhlman and Polcyn indicate that the american federal guidelines want 71C for roast pork, however they prefer the result from pulling it out at 54/60C internal.
They also remind us that the core temperature will rise another couple of degrees C after the cooking heat is removed from the exterior.
Hence their 54/60C gives an actual max temp of 60/63C, which they describe as "medium-rare to medium".
I'd expect this "carry-over" to be perhaps rather less with lower exterior temperatures than roasting (as with ham simmering).
The point I'm making here is that the 70C previously quoted is for cooking until "well done" - which may not be what everyone is hoping for with ham - and isn't written in tablets of stone...
(I believe that 71C in pork is one of the 'hurdles' to achieving total confidence in safety of food for commercial sale.)