I just read an article in Crappie Wold magazine in which several agencies were spoken to, including the TWRA. They said that PVC and other such materials should be used sparingly due to their longevity. They prefer habitat that will deteriorate over time. Also, the article said that man made structure can do more harm for the fish than good as there is no scientific evidence that man made structure do more than concentrate the fish allowing more to be pulled out and can hurt the overall population. That being said, I would love to help in anyway possible as long as the TWRA is included in all plans.
Also of note, they said the structures are more attractive for crappie, if it is standing timber as opposed to a brushpile and the less dense the better...