one thing i have found with yew, is that it is super prone to checking until it is properly stabilised.
i have had logs that have been cut for years, stored outside in an unheated shop, and when i brought them in to work on, the backs checked so badly,in less than half an hour, as to be totally unusable!!
now days i leave them outside in the unheated/ draft free/ shaded shop, then slowly bring them into progessively warmer and drier places.
splitting them will help a lot, and i like to seal the ends with wax- although i have found the end checking not as big a problem as the sapwood checking right down into the heartwood!!
good luck, sounds like some awesome pieces.
what sort of ring count did you get on them!!