I've done four-up in a 172 and in a Warrior and had no problems.
Be sure to do weight and balance calculations (because you almost certainly will not be able to take a full load of fuel).
Also do takeoff and landing performance calculations - particularly if you are using a short runway, or have obstacles near the field, or have a high density altitude.
I've found that a fully laden Warrior on a hot day does not climb very spectacularly.
In the 172 you may find that with the trim set in the marked takeoff position, the aircraft will gently lift itself off the runway when it's ready to fly, without any control input from you, and before you were actually intending to rotate.
If this happens and makes you feel uncomfortable , keep flying in ground effect just above the runway until the aircraft picks up a few more knots.
I've never known that phenomenon to occur in any Piper.