Hmmm. Well. I could be mistaken, but. I feel a root rake should have a rounded profile to the bottom ribs and the ribs running up somewhat form a circular side profile. With a top clamp/grapple in the half open/closed position it forms a circle a large log would fill.
The rounded profile allows for you to enter the ground tipped out and engage the teeth into the earth and forward and down pressure finds depth(and the roots, then forward and curling up rides the curve of the tines and up pressures uses all the torque and HP, and weight of machine, to rip THROUGH the root ball.
I say this, when I look at huge land clearing rakes, ( on crawlers or wheel loaders) that don't even have a grapple on top, they are using the rounded profile to levarge stumps, and they are only aiming to stack the debris for burning anyway, though they can and do lift and load without the grapple.
Rock buckets being flat, I use it more like a planer blade, that chisel shape lets me find the rock, get under it, and roll it up to the surface and sift the dirt off it until I can get it far enough back in the bucket that I have it when I curl it out of the ground. So the Flat bottom is good for that. The Flat bottom is also good ish to round up piles of tree debris..... I don't particularly need a grapple, and it can actually be inn the way if I want to back drag the holes I just created.
My root rake was made by Millonzi and is only 48" wide with six tines and I use it on my ASV RC-30. Raking tree roots is difficult, because I am engaging the whole width, when much of the time I only really want to engage 12".
Which is my real advice. Time working and how hard it can be on a machine should be a decision point. I clear very selectively so compact machinery is my need. I need to keep the trees 8" or bigger, ( and 20-30" specimens) but they are surrounded by juvenile trees 6" down to 3", and the roots wind up intertwined- and engage a full width means I'm into and fighting bigger roots I want to keep. I can usually push on the target tree to loosen/SEE the roots of the target, then focus an edge tine on just those three roots, maneuvering with a CTL is the only way. I would not use a Tractor FEL, Its sure way to break lots of stuff..... Not to mention falling limbs....
I really want a root bucket for my ASV RC-30, such as EA makes that is a single angled pointed bucket, but I have been bleeding money lately, and it isn't in the budget. Beinng a very small engagement point nd right int the middle, it will be easier on my machine.
My own land is an Oak Hammock. 0-1' is peat/duff, 2'-4 feet will be a gray clayey sand (very Sticky and will have roots) then the 3-5' layer might be white clayey sand which is very clean and a real nice consistent stickiness, then I hit the limestone boulderized layer that can be 3-4 thick. Below the limestone boulder layer is going to be either a coquina shelf or coquina shell, and sand.
There can be Limestone/Fossilized Coral on the surface to any depth.... I fetch them out one day and let them sit to let rainwater wash off the sticky clay dirt, or just dry off and retrieve later with the grapple... When digging in a hole and claiming the fill I separate/stockpile, once I hit the limestone in a layer, I move on. I can break through it with an Excavator or electric jack hammer if needed, but the water table has to be down. We are in drought now, so a five foot deep excavation is still dry and I am on the rock layer, water assuredely is right below this. IN normal conditions, I will have water in the hole, then I lose traction...…