I'm back on HF at home now. In March my Diamond CP-6 vertical stopped working, I think one of the traps had gone open circuit. Finally took it down on Monday and replaced with a 5/8 wave CB antenna (cheap 'Silver Rod' type) as I didn't have anything else to put up. I've shortened the top section a bit so it's tuned to around 29 MHz.
I can't compare this and the CP-6 side by side but on 14 MHz and higher, with a tuner, the CB aerial seems to be working as well as the CP-6. On 40 metres and below it's not as good and I've not even tried transmitting into it on those bands.