Small vent cover, what do I do?

I need a solution for a vent cover under bench seating we had built. See the pictures. The opening is 2x10", so I bought a 2x10" vent cover thinking that would work but I was wrong. The height of the vent cover is too tall. The vent can only be about 3" tall. So that's my dilemma.

I'm thinking I could cut down the vent cover to the desired height. In that case, my main concern is securing the piece firmly enough so it's safe to cut. I would use a jigsaw with a metal blade. I'd probably need to paint it afterward and maybe use something to soften the sharp metal edge. Does anyone have any tips to get this done properly and safely?

I looked for custom vent sizes and didn't see many options for what I need. If you know of an option, please share.

Thanks in advance!

 

You'd need to use tin snips to cut that. Unfortunately there won't be much left if you cut it.
I see them available at 3-3/8" tall. Will that work ?
2 x 10 floor register

 

Would be best to find someone with a shear to trim but if the smallest ones are still too big a pieces of perforated sheet metal could be used to make custom size!

 

It would have been easier before the base was installed but you could remove that section of base and install a 1x or something without a profile on the top so it would accept the vent cover/

 

I'm dealing with the same issue right now but with a bit more wiggle room. I only need to trim off 1/4". I'm going from a 3 X 10 vent to a 2 X 14 opening to make sure I get as much flow as possible.

You could also make your own vent cover out of some 1/4 plywood for a front, cutting vents out with a router or your jigsaw if you are patient.

 

I think I'm going to try the tin snips first. I should have enough space. Will this leave a sharp edge on the metal grate? If so, what's a good way to soften those edges?

 

You'd need to file or sand the edge down to get rid of the burrs.

 

Thank you all for your input. It was very helpful!