Is it possible to allow a custom property value to go as high or low as needed?
In other words, is it possible to make a custom property without clamping it with a min and a max?
Blender does not accept infinity as min or max value for a custom property directly, only with a trick. Usualy you can get infinity (of a float) by typing
What you can do instead is setting the min and max values to the smallest / largest possible number. I don't know a way to get these values in a number-field directly, but you can get them from the python console:
If you click on the number field Blender will however still show a number with 308 digits, so I do not know how the numbers are handeled internally.
Going off this answer, you can just input