Chill
Maybe the capitals gave the wrong impression there -----when I load duplex (dont use it much now) they are layered - I never tried mixing it - just more work again and I am inherently lazy.
Your second point is the most relevant one I think, duplex loading can make crappy blackpowder relatively easy to live with
Which gets to my third point - I make some nice willow charcoal powder that shoots clean so dont see the need for duplex much anymore
fourth point - my testing with decent quality powder gave better extreme spread numbers with straight blackpowder than with Duplex loads (it makes sense - why else would the hotshots that run things have ever allowed its use in longrange events ?!!)
I was surprised by the pressure data thats been quoted - I dont have any way to test that so had assumed that because I was seeing an increase in velocity over the chrony then it followed there would be an increase in pressure ? fair assumption as far as it goes ? and errs on the side of safety -- not the case ? thats good news!