Hiya,
http://en.wikipedia.org/wiki/Display_resolution
So yes it seems your correct at 5:4
So it looks like you're out of luck maybe, not being a ratio geek i don't know which to suggest other than 4:3 but obviously try and maybe ask for an edited version ?
Arclight's scopes support 5:4 but are not large as i recall, just edited to look very realistic (how compatible these are now with tdw's ui (i used them in the past @ 16:19) food for thought
http://www.subsim.com/radioroom/showthread.php?t=165408
Sorry i couldn't help further