C G D A, low to high. That is, fifths rather than fourths. For what it's worth, the late Red Mitchell, one of my favorite upright bassists, used to tune his bass like a cello, but one octave lower. He had some amazing hands.
I did that for a while with a spare bass. It made the Bach cello suites easier to play, but didn't do much else for me.
I've been using this tuning for 4 years. It's great! I've got the range of a 5 string on 4 strings. Chords are easier too (if it weren't a fretless ).
I've been trying to do them on my 5, but I'm going to change one of my 4s to that soon, should make it much easier.
