I too have a Stagg, two of them actually, and currently in the process of string experimentation with one of them to see what they are capable of sound-wise (when they finally arrive in the mail).
I'm not sure you'll ever get a truly double bass sound from it or any other EUB for that matter (just like you can't get an acoustic guitar sound from an electric guitar), but then a piezo-equipped acoustic double bass will sound different to an unplugged one or one that is mic'ed up.
It should be theoretically possible to get close to a piezo'd AUB with subtle EQing and the right strings hence my current investigation. As soon as I have an answer, I'll let you know.
I'm not sure you'll ever get a truly double bass sound from it or any other EUB for that matter (just like you can't get an acoustic guitar sound from an electric guitar), but then a piezo-equipped acoustic double bass will sound different to an unplugged one or one that is mic'ed up.
It should be theoretically possible to get close to a piezo'd AUB with subtle EQing and the right strings hence my current investigation. As soon as I have an answer, I'll let you know.