Is there a rule of thumb for double stops on the cello?

I am writing a piece for cello and piano and I'm wondering, is there any rule of thumb as to which double stops are easy and which ones are difficult on the cello? I know that for example an octave double stop is harder on cello than on violin, but how much harder? I have no experience playing a bowed string instrument, so all I really know is this:

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Some double stops are harder than others. On violin, a twelfth might be okay, but I should probably avoid that on cello, even if there are cellists that can play such wide intervals, not just because of how much bigger the cello is, but also due to more contrast in timbre in each octave of the cello's range. And with double bass, I can't even trust that the octave is a possibility, let alone know which octaves are more difficult than others. Thirds are okay all the way down to F2 as the lower note of the interval. Sixths, also okay, even with the lowest note being C2. But what about sevenths? Fifths(outside of open string double stops)? Fourths? Are fifths harder than sixths? Are sevenths easier than fourths? How much more difficult are octave double stops on the cello compared to the violin?

I have tried looking up charts of possible double stops, but I rarely find them for violin, so it would probably be even rarer for cello, despite the similar commonality of the 2 instruments. So, I can't just look it up online and write down the double stops in order of easy, intermediate, difficult, not just because of the rarity of double stop charts, but also the variability in the size of the cellist's hand. On the violin, this hand size variability is a non-issue, as most double stops an octave or smaller are easy enough. Not so for the cello.

So, is there a rule of thumb when it comes to writing double stops for the cello as to which ones will be easier for intervals other than thirds or sixths? Because, I have this harmonic moment here in my piece(which, by the way, is in C major) around bar 8:

I know the third is easy, but what about the preceding diminished fifth? How hard is that? You see why I am wanting a rule of thumb for double stops besides thirds and sixths such as fourths, fifths, and octaves?

What is the tempo?

how I can explain this... The stops should be play on each string without shifting. So can you play C3 and E3 on the C and G string respectively and then play G3 and C4 on the D and A string without shifting?   To my knowledge  No? 

As a general rule, most double stops are okay up to an octave. In the low register, many cellists use their thumb to reach the bottom note. As you get higher, the notes are closer together so larger intervals are easier.

2 hours ago, caters said:

Some double stops are harder than others. On violin, a twelfth might be okay, but I should probably avoid that on cello, even if there are cellists that can play such wide intervals, not just because of how much bigger the cello is, but also due to more contrast in timbre in each octave of the cello's range. And with double bass, I can't even trust that the octave is a possibility, let alone know which octaves are more difficult than others. Thirds are okay all the way down to F2 as the lower note of the interval. Sixths, also okay, even with the lowest note being C2. But what about sevenths? Fifths(outside of open string double stops)? Fourths? Are fifths harder than sixths? Are sevenths easier than fourths? How much more difficult are octave double stops on the cello compared to the violin?

Right, let's have a look at this.

1. Twelfths on violin? It's going to be extremely difficult. Possible in the high notes, but consider that a short passage of tenths in Tchaikovsky's violin concerto is considered one of the hardest double stoppings.

2. Good point about the contrast of timbre. However, string instruments are rich in overtones, so octaves blend better than you might think - the lower note reinforcing the upper and vice versa.

3. Double bass double stops are a no-no, unless one of them is an open string. Even then, it's going to sound odd.

Twelfths on Violin are impossible unless an open string is involved. Otherwise, violinist can only play tenths. 

8 hours ago, maestrowick said:

What is the tempo?

The tempo of my piece is quarter note = 65 BPM, though with all the sixteenths I am writing for the piano, it is turning out to sound more like an Allegro than an Adagio, making me consider changing the time signature to an eighth note time signature.

NEVER do 12ths.  My wife says more than an octave is a no-go.

Hello! I am new to the forum. I wish to becoming a contributing member and intend to add more of myself regularly to this forum.

I'm in my mind 30's, hoping to enter a master's program in composition; some of my challenges on the way comes with the fact that my undergraduate studies wasn't in composition, which I now regret later in life. 

Amid building my profile, I am writing a string quartet, which the 6th and final movement is enamored with heavy double-stops and triple-stop rolls and tremolos. 

I'm glad I came across this thread. For my inquiry, please observe the following cello passages mentioned in pg. 2 of my piece. Is this fast octaves-motif viably doable?

meter: 5/8

tempo: 8th=156