I wouldn't say iffy, but we certainly wold have neither wanted full tanks nor a third person in the plane. What adds to the excitement is that the old 172's Owner's Manual reflects rather wishful thinking than a realistic takeoff performance. It also suggests to add only 7% to the take off distance if operated of a turf runway, what also appears insufficient.
We therefore took a reverse approach and calculated, based on know variables, which were the climb rate at Vx + the height of the trees + a generous safety margin at which point we would have to be off the ground in order to make it safely over the trees.
What really adds to the ground roll and what is very hard to calculate and pretty much an unknown before the first take off attempt, is the condition of the runway. If it is soft, the grass long or wet, it feels as if the parking brake would be engaged. To define a point at which the takeoff will have to be aborted, therefore appears mandatory.
If there is no clear visual mark for this abortion point, time can also be used as a guidance. Even though not exactly scientific, to take half of the rotation speed as the average speed for the ground roll and to calculate the max. time which may pass within the distance to the abortion point, is sufficiently precise. Once the time is calculated, one just needs to count 1-1000, 2-1000, ... to easily keep track of the passed time.
Makes me homesick. (Also makes me wish I had a plane that's more short field capable. Those trees on either end would make getting out of there iffy in my Cardinal)
Not being able to get out of the 6Y3 was our main concern. We didn't have full tanks and nothing on board what we didn't really need for the trip. Our race horse made it in and out ok... 
