Here's an educated guess and fact for ya about horn and sinew from my experience with it.Putting that wood core in reflex first would of helped immensely.Like Pat said.Now you'll need to reverse brace it as the sinew cures.Helping the sinew.Your horn should be already on though and I would of grooved it together with the core too.You want to put the compression strong horn in reflex to relieve itself coming to draw and adding sinew as it's reflexing to make that sinew work when it goes into tension.You can start thinking this way about it.If you make each component core,sinew,and horn 1/3 thickness your core of wood won't need to do much work.More durability.I'm sure you realize this.You'd have to put it to a 6" brace from at least 10" of reflex.That's 16" of travel.Say you put it to a 6" brace to be cocked in your crossbow to 14".I know 3/16" thick of horn and 3/16" of cured sinew will give you close to 60#.30# apiece or more from 10" of reflex.That's on 48".Yours is 36".Your poundage will be a lot more a foot shorter though.I don't have a formula to calculate that,but my quess is you'll need 5/16"" thickness of each component to get your weight of 150# at such a short draw.I'm not sure of that either.Your crossbow will take at least 6 months for sure,and you'll have to add as you go and wait.Tillering should'nt be crucial at such a short draw but gettng it to brace will be a nightmare.I would use a pegged jig on a big flat board.First you'll have to get the reflex pryed apart flat.Your string will have to be about 20 strands of B50 for sure.
Now if this is your first attempt at sinewing you are taking on quite a project.
