The only two piece Shrew bow made with a BowBolt that has EVER failed was the one that was made for "Irish" as the St. Jude auction bow a couple of years ago. The failure was entirely due to the problems associated with the Gaboon ebony, not the BowBolt, the design of the Shrew, or the construction of the bow. There are now dozens of two piece Shrews with the BowBolt that have never had any problems. Gregg Coffey now insists on using at least a lamination of phenolic material in the riser to add the strength and stability to prevent a repeat of the one failure with the solid Gaboon ebony riser. The phenolic is an attractive alternative to Gaboon ebony without the problems that have been related in this thread.
Mike Westvang knows what he is talking about and has made a very informed decision not to use Gaboon ebony on future bows. The bow that I consider to be the most beautiful bow in the world, the Blacktail Snakebit, uses both Snakewood and Gaboon ebony in the riser -- two woods that are among the very worst for cracking and checking. Norm Johnson recognizes these problems, but continues to build bows from these incredibly beautiful materials. I had Norm build a Snakebit for me, and it is one of my prized possessions, despite its propensity for problems over time. Unless the looks of certain woods is your primary interest in a bow, I would steer away from some of them like Gaboon ebony. By the way, Snakewood laminations on limbs are not a problem because they are so thin they do not have a moisture retention issue.
Most of the true ebonies can have similar problems as Gaboon ebony, just not as bad. That includes Black and White (also known as Dalmatian) ebony, and Macassar ebony, both of which I love and which are used extensively for building bows. Texas ebony is not a true ebony and is very stable. It is more similar to bacote. Leopard wood looks somewhat like Snakewood but is not not nearly as striking; however, it does not have the problems of Snakewood because it is entirely different in its structure. Mike Westvang and other bowyers who work with the various woods all the time are the best people to advise you on the best woods to use in a bow.
Allan