Tim,
To me building the treegetter would seem easier than the shear which you built.
I would think you could (should) build or purchase a quick attach for your front loader. They are really nice & productive when you have more than one implement. I sometimes carry several implements to the field & lay them down so I can work a little bit with one, then switch to another.
I think one of the things that makes it work so well for me, is the hydrostatic transmission & 4 wheel drive. You can hold pressure against the tree while curling the treegetter. This just makes it bite in more. Also while picking up with the loader which give more traction to the front wheels & can put forward pressure on to lean tree over & tear roots out of the ground. I have even used the tips to stick into a larger tree or post, as if to gig it.
My loader specs say breakout force up to 3990 lbs. Rollback force up to 5025 lbs. lift capacity up to 2930 lbs.
Hope this sheds some light on what you may want to do.
Happy tree shearing.
PS: I have built a larger one for the rear 3 point, but so far am not as happy with it.