Damn, Working it Too Hard

The warbow flight bow for heavy arrows has just exploded. It was bending a lot in the middle, but I was happy with that, I was just getting the outer limbs moving and the tiller was looking good. It was braced at about 4".
I was exercising back and forth at about 100# at about 22" and started moving towards 110# to see the draw length at that weight when it went bang.
Bows normally go in the middle of the upper limb and I was keen to avoid that, which is why I was letting it work hard at the grip. I was also expecting the outers to look a tad stiff due to the hint of reflex.
Anyhow it's an interesting break for a few reasons:-
1. It's just above the arrow pass.
2. There is a bit of a waggle in the grain of the backing strip where the grain runs off the side of the bow.
3. There is a knot in the side of the Yew which also has the grain running diagonally across the bow.
4. The glue line has failed over a small area, indicating an imperfect glue up.

The interpolated draw weigh at 30" was about 147# so I was rather over weight and maybe should have taken it easy... but that doesn't really hold up.
It's a tricky question, of course the bow will have to pull to 120# at some point, but there are two things in play, the force on the bow and how much it's bending, either of which can break the bow.
I checked and I'd actually pulled it to 130# before, but on a long string and not at that amount of bend. It's always back to the same old adage "Always pull to full draw weight, as long as the tiller looks ok".
Of course actually seeing if the tiller is ok, is easier said than done.
Never mind I'll have a nice cup of tea :-)

I shall endeavour to learn from these lessons for the next highly stressed flight bow.