Machine guns:
Don't care much for any automatic weapon that jumps around as much as the different 5.56 derivatives. Most of them appear to be assault rifles on steroids. I had MUCH better results with the M-60 in medium to heavy undergrowth than with the 5.56. The M-60 is heavier but stays on target better and WILL cut brush. The 5.56 (at least the ones we were using) will not. The M-60 was also a very reliable belt feed and would shoot a LOT. We never bothered with the other barrel. Finally, an M-60 SOUNDS like a machine gun and that gets into peoples heads, your people and theirs... ;-)

Squad size:
Never felt the rifle squad was realistically designed to operate on it's own but as an administrative convenience to get enough infrastructure (Squad and fire team leaders) to let the platoon operate effectively. Maybe the all-volunteer thing has changed that equation but between rotation, casualties etc. there weren't many full to&e squads running around loose. When you start with nine and pare back from there for reality (rotation, illness etc), you got problems as a maneuver element.

If we were going out to ambush or interdict, we preferred to take 13 to 15 people. You need that many for a decent ambush if you are going to have any security at all and still have a decent KZ. Also some losses don't reduce your firepower in such a drastic fashion.

A TO&E rifle squad after R&R, illness etc which then takes a casualty or two is a fire team with lots of baggage and a seriously reduced ability to defend itself, let alone attack.

My 2¢