One of my basses has been tuned in fifths for a while but I never got around to playing it much. I've had a set of Spirocore Red Mitchell strings on the C-G-D for years and a Belcanto Solo A. These are my findings: 1. LOUD 2. Incredibly powerful 3. Lacks warmth for arco and a bit scratchy 5. C and G and quite slow to respond under the bow. I really like darker/warmer sounding strings like Belcanto - has anyone had any luck with a C and G that is a bit quicker to speak and a bit less growly/aggressive sounding? I will probably end up putting a Belcanto Orchestral D on soon.