No, I don't think that he was or is a dub.
And that, sadly, is largely where the story ends. Sly made comeback attempts in the late 1970s and early '80s, releasing three mediocre albums. P-Funk's George Clinton brought him on tour with Funkadelic in 1981; he also appeared on former Time guitarist Jesse Johnson's 1987 single "Crazay" — the title of which is so Sly-influenced that it verges on parody. The drug problems continued, with Sly being arrested three times on cocaine charges and ending the '80s in prison on a 55-day charge for driving under the influence of the drug.