Just mahogany or mahogany with maple top? I have HDs in a Les Paul Custom and had it in a les Paul Standard. I wouldn't say it's dark sounding. It's thick, with edge but more on the singing side that the hairiness you can find in a Rebel Yell, PKs,... I have to say that I love this thick with lots of mids tone and that I wouldn't say les Pauls are dark guitars (at least mine). Resonant, full sounding, yes but not dark.
I should also say that I noticed a significant difference between covered and uncovered HDs in my Les Pauls. I red many times that it should be a subtle difference but with the HDs, for me and in my guitars was more than subtle. I have covers in Rebel Yells, Mules and Painkillers, in mahogany guitars and never had a problem. But with the HDs I missed some edge. Taking the covers off was life changing. I guess that in pickups/guitar combination where the highs are not predominant, the effect of the tamed highs from the cover could be more significant.
I never tried HDs in a mahogany guitar whithout maple top. After my experience with the covers and HDs, I don't how how the absence of a maple top can affect to the overall sound. It should be darker, but I don't know if enough to make it dark sounding, without edge.
