I was recently wondering something similar. I said "Jesteś najmilszą kobietą" to a woman because it seemed weird to say "Jesteś najmilczym człowiekiem". This was after she complimented me for attempting to learn Polish (true story :-)). Was i right?
Probably yes, as it wouldn't resemble anything else anyway. But maybe it's better to make an a bit bigger stop between "jest" and "wspaniałą"? Also it may help to think of 'w' as devoiced and make it 'fspaniałą' in pronunciation.