Singing in the passagio

I found my "mix" a few months ago and am since then able to sing higher notes much easier than before. But the notes E4/F4/F#4 are still a problem for me. I'm not really sure how to approach them.I could either try to pull up my chest voice and produce a clear tone but a LOT of my strength in my abdomen is needed to hit it and i can't hold it very long. On the other side I could try to hit these notes with a "mixed voice feel". It feels much easier but my voice often cracks while holding the note or is really raspy. Singing the notes G4, G#4 and so on is much easier again when i hit them in mixed voice. Anyone got an idea?