This is an interesting observation, and not what I was expecting. Pirastro actually markets the Perp Stark G and D on their website as a string that blends "beautifully with the Perpetual A and E „Mittel“ or any other string combination where thicker G and D strings are desired."
I tried the Perpetuals before the Stark G or D came along, and have been interested in trying them again. Like Spiro Weichs, I loved them at first, then found that they were just too weak once my bass settled in. I am starting to appreciate the feel of slightly higher action on DB and the way it pumps up the potential energy of the string to create a more percussive attack to the note. I wonder if the lighter gauge may feel better this time around relative to the Spiro mediums. Maybe I just need to start lifting weights again.