Diesel Fuel sending unit adjustment

Just replaced the sending unit in the fuel tank and while the sending unit clearly works better than the old all or nothing unit it only reads up to just over half filled. I think the float is at the top of the tank and so i just need to bend/shorten the horizontal section of the float arm. Does anyone have experience with this? I just want to know if there is a concensus on how much to shorten it.

Thanks,
Rick

might be getting trapped on suction or return pipe ,might just need rotating a little or side of tank in one case i saw 180 degrees out

i will def try that first, Thanks!

Thanks James, you are a huge help.