Any question answered...

What tyre width and rim width?
You can temporarily over-inflate to get it seated, maximum tyre or rim pressure rating (whichever is lower) + 50% shouldn't do any harm.
Also, get some of this:

Tyre - 47mm
Rim - 19mm inside seat.

Max tyre pressure is 75psi so I took it to 90 and it made no difference, I'll try a little more. Can't find the max rim pressure. I may have to buy some of that stuff.