To have peace of mind I would back it.Dry it is brittle.You'll still get a 66" long bow at 47.5#.You'll get er.Takes heat bending well.Made a 64"black cherry a while back at 53#@28".It had a couple rings of sapwood left on.I backed that with sinew and snakes.It ended up holding a resting 4" of reflex.People are worried about the weight of this sinew on bows.That paticular bow weighed 16.50 ounces after sinewing but before handle wrap,skins,& finish.After 17.20 ounces.That's low weight.Very snappy bow.You'll like it.Makes the FG boys scratch their heads.
Got a 60/40 molly all heartwood 63" long that'll get sinew in a month or so.I'll induce reflex in that one too only not quite as much as my previous one.Old Gus give me a Texas red rat snake for that one.
I hav'nt had luck with red cedar but cherry makes it up for me.I'd put horn overlays on yours too even before tillering.The wood is softer if your used to making hedge bows.