Tim86 - I don't know enough about the details to give proper advice here.
The key question I would be asking is, do you really want to rely on shift work, and overtime, to make a decent income? I'd be looking for ways to get into managerial positions, which may initially on paper pay less due to no more o/t payments, but give you much more potential to grow.
I started in my company 20 years ago as a shift supervisor, and enjoyed the overtime/shift rates. I left it behind for a managerial role, made less income for a year or two, but then quickly leap frogged over those overtime incomes and now making 10 times what I used to make even with all the shift and overtime loadings thrown in.
What do the top managers make in your company and do aspire to it?