So long as it meets the regulations,
"Each character must be 79mm high and 50mm wide (except the number 1 or the letter I). The width of each character stroke must be 14mm. There must be a space of 11mm between characters within the same group, and character groups must be 33mm apart. For the purposes of measurement, each character (again, excepting the number 1 or the letter I), regardless of its shape, is treated as a rectangular block of dimensions 79mm x 50mm"
Then I dont suppose it matters if the plate is 8' x 4'.
Dont think it will be long before you wondered why you worried about your number plate.