Ive never been asked by a stranger to borrow a bass.
That would be a tough situation for me, as Im one of those softies that cant say no for some reason, especially if a bass player was in dire need.
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I usually play an unlined 5 fretless. That keeps most guys from wanting to borrow it

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) i had to play the support bands right handed one upside down....made of an interesting gig....in fact, heres a photo.