Never saw this thread before this morning, guess I don't search the site as much as I should.
First off, on that particular set up the Mike is showing, the bridge and lead strap are made from a Trophyline lead which is 9,600 lb. test and over the 20 or so years I've been using the saddle lead strap material for my bridge and lead, what little bit they have rubbed together when moving while hunting, you can't even tell. I don't think the rubbing together has compromised the strength at all.
And I have to say this, when TMA (Treestand Manufacturers Association) tested the Trophyline saddle, it withstood more punishment than any conventional stand they had ever tested because the strapping was way overkill concerning heft. They strapped a 275 pound log in the saddle, tied off the lead 6 foot above, lifted the log/seat and let it free fall the 6 feet and the lead strap not only didn't break or rip, none of the stitching on the saddle or lead, nor the adjustment buckle showed any signs of weakness. There is no question that you could use the saddle lead as a tow strap for pulling small vehicles out of ditches if needed. Of all the conventional treestands and climbers TMA tested by dropping a 275 pound weight on them from 6 foot above, they all failed miserably and collapsed.
For what it's worth I do use Cranford T-screws and screw them in at 45 degree angles (screwing it in at a downward angle is extremely important so that the lead is always tucked tight to the tree, even when you lean back farther away from the tree), however I do not use the Midget T they show on-line of in their catalogue. Cranford makes a longer T screw that is not in their catalogue or on-line and you would have to call Dennis (owner) @ 704-209-1817 and request them. The issue with the midget T is you can't them deep enough into the meat of the tree to be safe because at the 45 degree downward angle, the T portion hits the tree and doesn't allow you to screw it in deep enough for safety after all this T is supporting your LIFE. Of course in soft trees like conifers, poplars, cottonwood, and sugar maples for example, the longer T needs to be seated as deep into the tree as possible and I carry an 8 inch piece of conduit to tighten them beyond what I can tighten with my hand strength. I actually always use the conduit for all trees even though on hard trees I don't screw them in as deep. The second T that the loop goes over is also at an angle so the loop ends up tight to the tree.
Never use rod steps for this procedure as they as well only allow you to screw them in a specific distance before the side of the step stops you from going deeper.
If you're on property where you can use spikes, I would suggest using 8 to 10 inch long 3/8 diameter spikes or bolts and again drill the hole at a downward angle and drill at least 4 to 5 inches deep before placing. The drill a hole and place another spike or bolt to the side to drape you end loop over. Make sure that the hole you drill is a bit smaller than the spike or bolt as you want them tight. I usually have to tap them in with the hammer end of my hatchet when setting up with spikes or bolts.
When I originally showed Mike this set up, we were in his back yard and we screwed a Midget T (at an angle) just past the threads into a relatively soft tree and another off to the side for the loop hookup. I weigh 160 pounds and when I got in the sling (our feet were on the ground) and moved around the tree it was fine. When Mike got in the sling (Mike weighs a bit more than me) and began moving around, the top T screw that the lead was draped over began to drop downward because the tree was soft and the T wasn't screwed in very deep into the meat of the tree because it was a Midget T and could only be screwed in so far.
I had mentioned to Mike that might happen and it did. Now Mike is using longer T's and screwing them in all the way until the T hits the tree and is having no issues.
If this is not for any of you, you can use a rope/prussic as your lead and wrap it around the tree as normal, but what the T's do is make tree diameters irrelevant, if you can climb it, you can hunt it and that's a big advantage.
Another thing I should mention is that in the one picture of Mike sitting in the sling so you can see the lead, bridge and adjustment buckle, Mike's leaning backwards (only to show the set-up). At no time when hunting from any harness system, should you ever lean back in this position for any extended period of time as it will put a major strain on your back and is very uncomfortable. That's why I've always suggested to tie off the lead to the tree at or near eye height or even lower on small diameter trees as that allows your upper body to lean forward and be much more comfortable. I oftentimes lean my upper body and head into my lead, wrap my arms around the lead, and take a nap and you can't do that if your body is directly upright or leaning back. My lead is typically at a 45 to 60 degree angle depending on the diameter of the tree.
I think a lot of first time harness users have given up on harnesses for this very reason, they hooked up too high and were extremely uncomfortable.