The Solo Bass 55's and other "Pressure Wound" strings will cause less / much slower fingerboard wear on a fretless.
I haven't used the 55's, but have used Compressors (Pressure Wounds from Ken Smith) for a while on my unfinished ebony board fretless (I ended up switching to rounds and have been using them since and they really don't dig up the ebony all that much).
This picture kinda gives you an example of how the outer windings look... they are less aggressive than the standard round wounds since the outer windings are more rounded on the surface. Less finger noise on these too... The picture is of "Ken Smith" strings... Round Wound / COmpression Wound (Pressure Wound) / SLick Round (half-rounds)... Very similar on the 55's.... (workin on getting pictures like this of various strings.
