Some blokes tape the fastening like on the right here, which is better than how you have yours Lerch as it stops the toggle flapping about, but also provides more tension to keep the middle toggle in the fastening loop. Even then it only tends to be your left ammo pouch like this, where you might need access in a hurry, otherwise you would do them up properly as bluffcove says.
That's the way I do up mine. I always use the velcro as well. If I'm worried that someone is close enough to hear me open a pouch, then I'm hardly going to take a long swig of water...
I reckon I might get my ammo pouches modded up with those long velcro strips....ah, the Sunday night kit musings. It's time like these that you realise you ought to text your muckers and meet them down the pub!
Anyway, totally changing the subject from the exciting world of pouch fastening, does anyone know who makes a DPM chest rig with three double mag pouches across the centre, with 3 40mm grenade pouches either side? Will post a pic when I get round to it, but bought it off ebay for about £5 (bargain) and was wondering if anyone here knew who actually made it.