Marion, et.al.

Agreed on the double stops, although it is a limited selection. Food for thought: is it the selection of doubles available on open strings that makes a certain few keys "fiddlers favorites." (I've heard answers, and they're not too relevant here.)

And as long as you're playing "chops," a bar may be okay. The problem with a bar fingering comes in mainly when you try to mix the doubles in with a quick melody. Fine if you can do it and get the result you want.

Since the crown of the bridge prevents most bowed instruments from playing more than two strings at the same time, the reach problem for "chording" (such as it is) is not too severe, even on a large(r) instrument, regardless of the tuning. It's when you try to play a "full" 3-note chord that, no matter how you turn it around, 2 of the notes you need are on the same string - unless you resort to "strange" inversions, when the strings are in fifths. It does make a difference, sometimes, which side up a chord is played.

Bowed instruments don't have quite as much problem with retunings as the plucked ones, since they don't have to have their normal tension up to near breaking where they "ring." You can always add more input with the bow, where once you've plucked - that's all that note's gonna get, so you have to be sure it "gives it all back."

You can probably detune a given fiddle or cello string further than you can a guitar. The resulting tone may suffer some, but within reason you won't be as likely to break the strings. On the other hand, I've seen some comments from fiddlers that the strings "go dead" a lot quicker if the tuning is changed too often; but the mythology of "good string/bad string" is a little beyond me.

There is also a relatively high string angle at the bridge on most bowed instruments, so retuning too much higher can put large (relative to normal) downloads on the top plate.

John