If you want a personal opinion, I say Tilia x euchlora still fits best, in my mind at least.
There's photos of the structure of the way flowers are held as can be seen in the photos of T. cordata which can be enlarged .. they look to be in flat almost umbels, more compact unlike those on yours which look more splayed as in a cyme.
http://luirig.altervista.org/c...
http://luirig.altervista.org/c...
That is only my opinion though.
