I like it! In general, I think that 2-syllable first names where the emphasis is on the second syllable (such as [name_f]Sinclair[/name_f], [name_f]Marie[/name_f], [name_f]Nicole[/name_f], [name_f]Cosette[/name_f], etc.) sound good paired with another 2-syllable-second-emphasis name as the middle.
[name_f]Sinclair[/name_f] [name_f]Cosette[/name_f]
[name_f]Sinclair[/name_f] [name_f]Capri[/name_f]
[name_f]Sinclair[/name_f] [name_f]Noelle[/name_f]
Of course there are other types of names as well!
In general, I think [name_f]Sinclair[/name_f] is a cool name. It’s easier to picture in the middle slot, but it could also make a very distinct first name.