I run in Newtons, either the original 4 lug Distance or the Elite; have been for several years, they have worked very well for me after trying loads of other shoes. I have very flat feet, which I deal with with scaphoid pads under the insole.
The reason I am asking is I am up to 20 mile runs thinking about a marathon next month, and I am feeling it in my feet toward the end of those runs. Would a lightweight aftermarket insole provide noticeably better cushioning?
I want a completely flat insole as I will still add the scaphoid pads, and I was hoping to not add much if any weight. Searching around, I found these 3:

Sof Sole Thin Fit

Sof Sole Athlete

Sorbothane SorboAir

Anybody have experience with these? Others to recommend?

Thanks,

Brian

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Brian

Gonna buy a fast car, put on my lead boots, take a long, long drive
I may end up spending all my money, but I'll still be alive