Die, Vecna, Die! Milestones for 5th ed

[Drinnik Shoehorn]

My Curse of Strahd game should be wrapping up in a few months (2-3 at the most), and I want to run Die, Vecna, Die! as a follow up eventually with the same characters. I’d like it to go to 20, but realistically would be happy with 17, so I need at least 7 milestones for them to get there (milestones are what I’ve used in CoS so I think switching to XP at this stage would be a bad idea).

I can think of:

1) applying the first of the vestiges of Vecna in Tovah Baragu
2) making it through Tovag Baragu and getting into Cavitus
3) making it into the Temple of Vecna
4) Arriving in Sigil

I’d like it if they were 16-17 when they arrived in Sigil.

Any suggestions?