I dont think any decent 4" will fit without any trimming. I am running the Focal 100 KRS up there which are a slim and fairly small 4" speaker and trimming needed to be done.
for reference:
Its not a lot of trimming though, totally worth it IMO. Another option I was playing with was some Hertz HL70, which is a 3" and would need an adapter to fill the hole, but I decided to go with the larger Focals for a number of reasons.