I've done a lot of reading about lab testing of woods and have "trapped" a lot of bows, ash in particular. It seems that wood stretches only about 1% of it's length before breaking without yielding first. The only clear gain from "trapping" the back is in the reduction of mass in the limbs.
That is a gain, I admit.
As for ash being stronger in tension, every wood is, though some are worse about giving no warning before a catastrophe. In fact most woods are 3 to 4 times as strong in tension as in compression.
My most durable ash bows were about 2-1/2" wide at the fade and 1/2" or a little thicker throughout the length of the limb. For a 28" draw, I always start with 66" ntn.