The gravity zones in forge are generally fairly limited, due to not being able to resize them. I have seen a few complaints about it on the forum.
However I came up with a few solutions.
TIPS FOR MAKING THEM SMALLER/ADJUSTING SHAPE:
Use the 10X10 or the 5X5, but then insert a “TRAIT ZONE” (which you can adjust the size of) to the area of the gravity zone you DONT want to effect players.
Then change the trait zone property in the forge start menu and change the trait zone property to ‘player gravity 150%’
This will give the players normal gravity within the area of the zone.
TIPS FOR MAKING THEM BIGGER:
Simply use a trait zone instead of gravity volumes and adust the player gravity in the settings to 50%. This doesnt effect vehicles though.
TIPS FOR NOT HAVING TO DOUBLE UP ON GRAVITY VOLUMES:
Insert a trait zone overtop the gravity volumes with player gravity 50%, this will allow the player to still be light enough to float.
This does not work with vehicles. You will still ahve to double up on gravity volumes with vehicles.
enjoy.