I'm sensing a major disconnect here.
Using advanced climbing gear to get to the top of the tree but don't know how to tie in once up there?
What hitch are you using with the rope wrench?
Yea, me too; with all due respect, runderwood, stop and start thinking from the beginning about this tree after taking a few deep breaths to max oxygen saturation and clear your head. I have learned to climb from my own experience (for the most part) over the last 25 years, and yet I have learned a lot from my climber I hired recently. You can always expand your bag of tricks -- it can save you time and your life.
I'll just make a you a list; over time, you will automatically run through it.
Visual check: tree
lean, tree species, defects (roots, butt, trunk, crown), height, lean and direction of weight, targets, hazards like wires (which may be attached to the tree!), drop zone
Visual check: gear
two lanyards (at least one wire core)
lifeline (clip to back of saddle with your tie-in knot on a biner)
figure -8 or the like
split tail (for friction knot set-up)
or: hardware for single-rope technique
harness
hand saw
wedge pouch
saw (you will likely top the tree with the same small saw you limbed with)
Site:
ground man in position,
ground man knows plan,
any rigging set up
any needed equipment laid out
safety barriers in place
plan for managing public and homeowners
That's before you get off the ground -
That's all before you get in the tree.
Once your feet are off the ground, you go over the tree, gear, and site checklist again, you also
go over a tie-in checklist:
all knots properly tied and dressed,
straps and lanyards adjusted,
biners, ascenders, and clips all snapped shut
(repeat when you go on your lifeline, switch from one lanyard to the other, or change over among arrangements on your lifeline including ascenders, other hardware, a friction hitch, a figure-8)
I'll let someone else continue with climbing, cutting techniques, rigging, and rescue.