Need Help another dumb question about letter returns.

[0igo]

Another dumb question lol. I think this one might involve a trip to my other home aka home Depot lol.

Okay so I'm doing channel letters (no lights in them & they will go inside a building.) Since I didn't bend and edge on aluminum returns to apply some pop rivets. What glue or adhesive can I use to make a strong bond? I don't want these falling on someones head unless it's my ex then idgaf ha.

The E below is an easier letter. Letters with curves is going to be a lot tougher.

 

[0igo]

Any way to join the corners on the aluminum and AC cut letter?

 

[KMC]

you could go old school and router the backs out of 1/2" or 1" PVC and screw the sides into it