I've used a microlite standoff for years. Mainly used for resting on roof tiles for easy access to rooflines and never had one come off a ladder yet. It was designed that way and is the only class 1 standoff that I know of which is also approved by H&S so in my book is the best standoff you can get in the UK.
For occasional use I couldn't justify spending £160 for a microlite ladder standoff tbh.
Spruce are you kinding me as that Ladder Master looks a total bonkers idea let alone wanting to use one 
Honestly Smurf, it works well. One of the local windies used one for years before he went wfp. I don't know about now though.
We had a local roofing company out replacing our dormer roofs with GRP last year. They used them. I asked where they got them and he got me a new one.
I didn't know what they were called until the roofing guy got me one. The name sticker was long gone on the local windies one and he thought it was called a Gutter Mate.
I patched our dormer roofs for years before getting the job done properly. I shaped a piece of 3" x 3" wooden fencing post and dropped that into the gutters which did a similar thing - keeping the gutter from 'collapsing' under my weight and that of the ladder.
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