Yeah, I wouldn't use that. It's pretty, but not really practical. Stuff will get caught on it, it'll get scratched and banged up and look like crap pretty soon. The formed piece of sheet metal and Pop rivets is the best way to go. How often do you need to get to the sending unit anyway?
There, you have it from a (sheet) metal worker...
Does this stuff every day, all day long!
With Jim_Lou, I'm surprised he didn't recommend you use STAINLESS STEEL!
One other thing I would do before you button up that hole!
Take those connectors off and coat them with dielectric grease!
Fill up that boot until it squishes out when you push it on the connector, then wipe down the excess!
Moisture LOVES to creep into those boots and terminals!
I actually SOLDER/SEAL my connectors on before I install so the connections CAN'T draw moisture and rot out!
Since you can't really solder around a FULL gas tank,
You should settle for grease and/or that liquid electrical tape stuff...