Buy the correct parts for the right frame. Why are you trying to run the gear changer up the seat stay? If you had the correct fitting kit it would run along the chain stay as Shimano designed to be fitted.
You could try to see if your LBS can order the correct non turn washers via Madison, or you can try bodge on a £400 hub and its fittings. For the sake of £15 you get the right bits to do the job correctly.
I’m openly admitting that I didn’t know the significance of the coloured washers before I bought the hub,I’ve never fitted one before. If the no turn washers were available from Madison, which they’re not, that would have been my first thought, which it was. My LBS has told me that Alfine fitting kits and spares are like rocking horse poo. I’m not looking to scrimp, just have the correct angle for the gear arm which matches the cable routing on the scandal frame i.e up the seatstay. Anyway, I,ve found the correct washer on my travels today, which incidentally is silver, thanks to the kind people at On One who had a grub through their nuts and bolts tray.