(Acrylic) Fill in gash in acrylic sheet?

[DarkSky]

I recently purchased a used 220 gallon acrylic aquarium, I've been spending a few weeks cleaning/sanding/buffing it to bring it back to looking crystal clear, the only issue is there are two 1" gashes near the back of the tank, they're about an 1/8" deep at the deepest, so they're too deep to sand out without making a fairly large concave section in the acrylic.

Is there something I can use to fill it in so I can sand and use Novus to make it look better? I'm sure I could ignore it, and it might not be that visible when under water (it's on the inside of the tank) but if there is something I could do I'd like to know.

Thanks in advance!

 

[Fudsey]

I'll tag @Elder1945 as he works with acrylic, for an answer.