The vinyl 'decal' (sticker) should be 'approximately' 25" (63 cm - is that right?) from tip of tail to top of crown. Either red or white.
Dude, you're in SoCal. half of the commuters on the road will be lookin' down onto the roof of your Alfa from their big, stupid SUVs . . .. . . installing an, ahem, serpent eating a Saracen on my sunroof. Since there are more than a few flying about, figured helicopter pilots might enjoy it.