I like to play in drop-D, for a variety of reasons mostly involving the use of a low drone string, simplicity of fingering certain chord-shapes quickly, and I like some of the interesting possibilities with regard to open strings and minimal fingering, especially high up the neck. I play largely by ear, and like to improvise a lot, so it's really important the intonation is very accurate. Even though other people might not hear the difference, a little bit off and it gets confusing as to where to go next, and isn't pleasing when you go to let something really stand out and it's just wrong to my ears.
On my electric I have adjusters for intonation, it's 24 frets, easy to play, and sounds great. But it's not always convenient, or easily portable, and it's precious to me. My acoustics are, well, cheap. I've tried lots of things, but always seem to be a few cents sharp at the 7th fret on a drop-D 6th string when tuned accurately with open strings. Or tuned accurately at the 7th fret, flattish when open.
I've tried modelling a saddle that mimicks the positioning on my electric, adjusting the nut, even using screws, toothpicks, or anything about the right size and shape to wedge in there, on either end, to get the intonation right. I've come a lot closer, but still a bit off, which drives me nuts.
Anyone out there with experience adjusting intonation on an acoustic guitar for drop-D tuning who might have a word of advice that doesn't involve spending a bunch of money?