10 meter, and not in the midle of the groups, and pouf! they are all supressed, and we can't make them "run for your life" in real war, if an officier said "evryone retreat", all the men will run away, not stay there and wait 30 second before moving. bomb fall, it will not take you 5 second to continue, but less then 30.
I have friends who've been in convoy ambushes in Iraq, and a couple bombs can paralyze entire platoons. Whoever fires first or with the biggest guns has the advantage of surprise, which tends to freeze our fight or flight reflexes for a little while.
I still think the best solution is a sliding scale that would act as a decimal modifier on the suppression times, so if you want to, you can have anything from practically no suppression right up to the present scale, or anything in between. That way it wouldn't affect any of the other content in the game, just a few lines of code to add the option in the menu, and add the variable to the places where the calculations are made.
Oh, and as for infantry damaging tanks, I think there should just be a small, random probability when tanks and infantry come upon eachother for the grunt to jump on the tank and toss a grenade down the hatch. I know it would change my tactic of pinning the enemy with infantry and then running them over with armor.