I really like the name [name]Tess[/name], but I’m wondering if people will always say"You mean [name]Tessa[/name]?" Is it to short to be a name? I like it over [name]Tessa[/name].
I actually think [name]Tess[/name] sounds more substantial than [name]Tessa[/name]. [name]Tessa[/name] would make me think, “you mean [name]Theresa[/name]?” whereas [name]Tess[/name] sounds complete. [name]Just[/name] my opinion. 
I love [name]Tess[/name] as a standalone. Yeah, I think she would sometimes be asked if it’s short for something, but it’s not hard to say “No, it’s just [name]Tess[/name].”
On another board, I knew a mom who loved [name]Tess[/name] but went with [name]Tessa[/name] for the birth certificate–she was afraid [name]Tess[/name] didn’t have the legs to stand on its own. She said she was so frequently asked if [name]Tessa[/name] was short for something, she wished she had just gone with [name]Tess[/name] in the first place.
I actually really like [name]Tessa[/name], and if I end up using it on my future daughter, I’d probably end up calling her [name]Tess[/name]. I don’t like [name]Teresa[/name]/[name]Theresa[/name] at all (it’s my mother’s name) and so I’d like to just call her [name]Tessa[/name]. I think either one of them could stand by itself, it doesn’t really matter.
I love [name]Tess[/name]! I agree, it seems more grounded than [name]Tessa[/name], which seems overly airy and with no substance. I would totally use just [name]Tess[/name].