But I do own a Warwick Corvette fretless 5er and been testin' an Ibanez SR505F many, many times to decide for a purchase.
While Ibanez is a lined fretless, and well, as you may know, sleek, balanced, resonant and so on, it was not my choice, but Warwick instead (which is beautiful ebony unlined one)
'cause its precision and accuracy blew me away.
I found out I'm more precise and accurate on Warwick ebony unlined fingerboard than on many other I tried out before, only
exception being Fender Jazz fretless
I play a full step downtuned and, let Squier Vintage Modified Jazz alone (really poor agathis body and ebonol fingerboard), even if I love Yamaha TRB1005, its lined fretless version was not only uncomfortable but absolutely misleadin', IMHO.
Fender fretless Jazz, by converse was fully adjustable, it held downtunin' quite fine, was factory equipped by proficient Fender flats (I then on happened to look after them over d'Addario Chromes) but I somehow failed to grab one on time.
It was bought right away by somebody else instead
Warwick is an alder body, maple neck bass (much like Yamaha TRB1005 and Fender Jazz) but its ebony fingerboard is as easy
to handle as it can get...
€. 400,00 for new B-E-L-I-E-V-E M-E
Now: I read your thread... lookin' for a fretless 6er... Take a look in the Warwick camp