I agree with these two posts.
I have not seen anyone run Rebirth solo. If you would like to see if it is going to affect your T/E ratio, then you would need to get bloodwork.
Letrone is powerful AI that will reduce estrogen, which means less water, which means tighten up some. Exotherm is a great non stimulant topical fat burner that can be stacked. It can also lower estrogen as well. If you feel like your estrogen is too low with the combo, you could also use Exotherm at a full dose and then run Letrone at a half dose.