Decreasing weight on mixed voice

[electricthunder95]

So I'm trying to sing this song called "Gethsemane" from the show Jesus Christ Superstar. I'm a rock tenor, so most of it I can do, both stylistically and range-wise(the whole song, but especially the high C near the end, is super fun to sing), but the part this song is famous for, and the reason I'm trying to sing it, is a high G5(or G an octave and a fifth above middle C). Famously it's done by Ted Neeley, who I think mixes it and adds distortion, Ian Gillian, and Steve Balsamo, both of whom do a really masky falsetto with heavy vibrato to get power on the note. My problem is that I can get the G normally, but as soon as I warm up my chest voice to sing the rest of the song, my falsetto and my mix becomes nearly unusable and I lose the high G unless I strain like crazy. I think it's because of weight on the vocal chords from singing in high chest voice. Does anyone know any exercises or techniques to help with this?