Haven't tried this, but my concern would be melting the eVent membrane, protective layer (essentially very fine NoSeeUm mesh bonded to eVent membrane) or face fabric and the microfleece using an iron hot enough to activate the adhesives. Although, if the temp needed to adhere is less or the same as temp recommended to refresh DWR of garment by iron, then it should be safe.
I've used non adhesive Velcro and glued it on using a dab of McNett Seam Grip. It will hold up to much abuse (I use it to repair peeling seam tape on my eVent jacket and add Velcro closures to open pockets).
Just dab a bit on the Velcro, let it sit a bit and get tacky, then press it into fabric and clamp/clothes pin or whatever to keep pressure until it dries. Plus, you'll now have a tube of Seam Grip for future repairs and projects if you don't already.