why don't you trace the back profile, and draw it a bit further each time to see where it begins to take set?
whats the point of this?
If you trace the back profile (unbraced) against a chackboard, or some cardboard, you can then brace and draw it to, say, 23" a couple of times, unbrace it, and then compare against the profile you traced. If it has taken any set, you will have to reduce weight, in order to be able to draw it longer. If it didn't take any set, then you brace it, try drawing it another inch, unbrace, compare, and so on...
The drawlength where it starts to take set is the longest you can get at that thickness, if you want longer draw, you will have to reduce weight.
However, with a 45 inch length, it will stack A LOT at a normal 28" draw, maybe even slip out of the knocks. So you will probably have to flip the tips no matter what, if you want that drawlength.
Hope that helps explain