The mag slots are designed to hold mags with max dimensions of 1.5"W x 1"D x 6"T.
There are 2 rows 2 columns of molle on the Triple Stacker M4 Mag pouch.
This pouch can go on it but my be a bit heavy fully loaded with mags.
My recommendation would be using single pistol mag pouch if you are going to kangaroo them together.
Any questions, just let us know!