while ive never tried velvets, i have had gamuts on one bass for several months now, and am trying different guts on another bass. i have pistoy's and i have a medium G and a light D. this is the setup i would recommend. even with the lighter gauge D string it still seems extra huge compared to the G string. its bigger than my steel A string. i can only imagine how huge a medium D string would be, and im not sure how useful it would be in the upper registers. as it is, the light D string perfroms well in the upper register, but you can hear where it gets a hint of thuddyness. i imagine it would get worse with thicker string. the D string is notorious for being the difficult one. if you look at the carlos chorda set, the gauges match the gauges of the medium pistoy G and the light D. also, there is a thread somewhere that mentions the ideal gauges for each string to get a good balance, and they very closely match the medium G and light D pistoy gauge.