I haven’t yet. I may not, actually. Although I haven’t done so with TS-E 17, with the 24mm I have occasionally stacked a CPL onto the ND, and that's something one cannot do with the drop-in. Here's an example from Luzern, Switzerland with the TS-E 24:
"Kapellbrücke"

EOS 1D X, TS-E 24mm f/3.5
L II, 30 s, f/5.6, ISO 100 (10-stop ND + CPL)