Tiger class and Fiji in effect had the same hull, in general. The idea of converting a Fiji, or a Tiger cruiser into a SeaSlug armed ship was rejected for various reasons, last but not less important, being money. The Tigers were rejected also because they were new, with a new gun which the Royal Navy wanted to test. The Fiji class (and to a lesser extent the Swiftsure class) were deemed to be too small, given the limited number of missiles, on a hull bigger the a 'County' DLG (than known as GW57 (?) still in the planning stage), and weighing nearly half as much as a Fiji.
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Thank you Kim for the crest
"Never fear to try on something new. Remember that the Titanic was built by professionals, and the Ark by an amateur"