To get rid of the spongy feel in the brake lever, I've today installed steel brake lines on my F1.
It's a ready set from HEL, consisting of 3 lines.
It is already a big improvement. I've put a tie-wrap on the brake lever to keep it pressed over night.
So when I'll bleed them tomorrow, for sure all air is out.

From the website, both directly at HEL UK as well as the Dutch company where I finally ordered it,
it was fairly difficult to make the right choice. I had the impression that they mixed various F1 series.
In the end it seemed to me, also checking the parts manual, I should choose the "Montjuich" set
for my 1988 F1.
The Dutch webshop did sent me an e-mail to check all dimensions to make sure, saying this
was their policy before sending brake lines for older types of bikes. Probably a wise thing to do.
Anyhow, it confirmed I had made the right choice.

With the fairing removed, I noticed that the lift side bracket for the oil cooler is broken.
I'll see if I can fix it or make a replacement.
Or somebody might have one available?