RGB combine: how can I ensure same dimension size and bit depth

Hi,

I´ve searched around at google and the forum, but I haven´t found a good solution for my problem: what is the simplest and best way to ensure same dimension size and bit depth, when I use the rgb combine tool, to combine rgb, ha, oii, oii and hbeta? 

I´ve used 4 different filters with dither and integrated them per channel (rgb, ha, oii, oii and hbeta) and now I would like to combine them all, but because of dithering the dimensions are different. What is the intended workflow at APP to solve this? Should I use mode reference or crop per integration? Or is there a simple way to align all images with the same crop?

Thanks in advance.