ozark...you have discovered one of the primary criteria, not only is grain orientation essential, but density and weight is key as well. As you found in the purpleheart you will also find in many of the exotic wood species.
I disagree with the notion that the turkey is in the lid only. I couldn't say how many box calls I have built over the past 10 years, but I constantly switch lids on bodies and visa, versa. When one lid works on one body, it won't on another. Without great tone wood in the body it doesn't matter what lid material you use, it won't work. With a great block of Butternut, Poplar or Black Limba many different lids will work simply because that block of Limba has the characteristics needed. You can have a great Bloodwood lid, but until you find the best block of Butternut you won't have a great turkey call. The two are not independent of each other IMO
