The correct JCV file type for 7x5 is 480 x 270 pixel picture size full screen.
For current EU [non-unicode] 2016.10 map that's either 329,328,366 byte D3084160A.JCV or 698,898,596 byte D2504190A.JCV but not both. D2504190A.JCV has over twice the images contained in D3084160A.JCV so only use the smaller if there's space limitations.
For latest NA 2016.20 map you can similarly use either the 858,343,775 byte D3060190A.JCV or 272,960,967 byte D3080190A.JCV.
But here's the thing, you may also use the NA split-screen 504,027,567 byte D3191180A.JCV meant for 2/3xxx etc devices in your 775 [but not the NA one for Android or xx nuvis]. That has at least as many views as D3060190A but at 212 x 234 pixels picture size it's a much smaller file size. That saves space but the JCV image display in a US/EU 1xxx/7xx/8xx device using a split-screen file will likely be stretched to fit the screen and show a bit fuzzy because of lower resolution, e.g.:
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