Don't know whether you'll find this helpful.
I've got a "Rojak" which gets used on one or two jobs. One in particular, which is a "double fronted" house directly at the edge of a pavement; the Tarmac has a steep slope down towards the kerb, but the pavement is too wide to place the ladder stiles in the gutter.
Only had it slip once, and that was on Thursday whilst at a new job. I put it on some wooden decking which has a covering of green growth - very nasty!
and,
The top of my ladder always wears a "Wickes" stand-off; it is fitted with two rubber pads which,
a/ allows me some space between the glass and the ladder top, thus eliminating the "Spiderman" effect, eg being pressed against the glass, having run out of ladder before running out of window!
b/ provides friction on the wall.
c/ can sometimes be placed [wedged?] immediately below the sill, and reduces the likelihood of sideways movement.
d/ allows access to windows above those bays that have pitched roofs, the ones where the ladder rests on the gutter of the bay before resting on the brickwork above.
Baldeagle in Staffordshire