I build a lot of serviceberry bows, since the tree's an introduced runaway pest here, and a super bow wood at that. I never chase a ring or back serviceberry, and I've never had a tension failure with it, no matter how high the crown was. I haven't built any with a 7-inch reflex, though. I shoot for app. two inches of reflex before tillering, achieved by cutting the stave off the tension side of the trunk and freeform air drying, occasionally tying down the unruly ones to keep the reflex at a manageable level. Serviceberry is so dense it dries slowly, about twice as long as the lower-density species I use. Ends up bone hard, too.
My serviceberry bows are sapwood throughout; on healthy trees the heartwood is apparent only as a drier, therefore whiter zone in the freshly-felled tree's cross-section, with the wet, thick sapwood dominating. After getting down to around 15 mm thickness at midlimb on the finished bows, what non-differentiated heartwood there was is gone, anyway. Low set, high cast and durability with all sapwood.
Tuukka