Nikk, there’ll be a gap at the back but it’s not open- it’s against the fork so closed off anyway. Or at least, this is how it works out with my Cane Creeks.

The Hope seal doesn’t seem to be too good at all tbh, it was more of a shield than a seal on mine, didn’t really make contact with the cups. But still, those pics show one seriously grotty headset, top and bottom!

I used a spare stem. Seems to have worked.

In the end I heated it up and it slipped on with a couple of taps. Job done!