just like split firewood- it dries quicker split.
the tree in the round has evolved to resist moisture loss. roughly 1 year to dry per inch of radius in the round( obviusly dependant on species, conditions etc.
split it, seal the backs and ends, rough shape it a little, it will dry way quicker.
i have seen that you cant rush the moisture out of yew- it then seems to check on the belly like crazy.what they do here is let it drop naturally down to about 15% or so then you can chase the last bit out with a hot box etc.
how thick is the sapwood on the back.
ideally you only really need about 1/4" although i have seen bows with a whole lot more.
the one thing about yew is that seems to vary so hugely.
if it was way to thick, i would take it down with an angle grinder and sanding disc, still trying to follow the general undulations, then back it with rawhide or silk, to counter the ring violations.
which ever way get the bark off now- its will be easier now, and seal the backs well with something- you will have to get it off for the transfer anyway.
alternatively, sell it there as it has real value there- no hassle for you- and you are doing them a real favour too!!
trade it for bow or something.
then when you come to take this pesky bear of yours home, you can take some yew with it.