Green Dot USED to be listed as a potential 20 gauge 7/8 powder when pressure was measured with the lead crusher method. From what I have read two things prompted the removal of those loads from the manuals. First the newer piezeometric measuring devices showed higher peak pressures than originally suspected and secondly skeet shooters using sub gauge tube sets were cracking 20 gauge tubes with Green Dot reloads.
If you are using them in an actual 20 gauge gun you should be ok. As 3Macs1 says, we need to know exactly which Remington hull. Take one, section it with a hack saw and post the picture. We can then suggest a load for you