Sorry Ralph,
We're not much help here...
I've got a NP boom, adjustable length, no probs, I can't comment on the chinook booms, but Chinook seem pretty popular. I haven't noticed much twisting, some of the cheaper brands tend to twist, but I think it's more to do with the poor clamp setup rather than the "removable arms"?
Probably not overly helpful, but I felt I had to contribute something after my poxy last post....