I took my selfmade porty up in the tree a few times, as in special circonstances. It's like the big version, a bit heavy but very doable. It is usually when working alone, when there is a good risk to hang the limbs on the way down, like in a big crotch between two coleaders. The advantage is coming on the blocage from above, not having to climb up again and fight the mess to pass through it. When it gets stuck, I come down while holding the tension on the rigging tail, ty it somewhere in the suspended limb, cut the bit holding it all, get out in the open air along the limb and lower it while coming down myself to ease the slide along the trunk.
I've done it inverted too, with the porty tied on the limb and the working end of the line up in the tree. This way I can follow the limb, while keeping the porty at hand reach, stop it, work on the limb like passing some keeper trees, and continue the lowering.
An other fun technique is like some sort of drt in rigging. It was to lower some heavy pieces in an old pollarded tree but with just some skinny sprouts as a tying point. No way to double the load with a block on that. So, I tied the block on the limb, hung the porty upside down on the rigging rope's end with the shackle, as in absolute floating mode. The rope went up to the tiny crotch, down to the block, up again to the porty, finally tied as usual. The porty was just above me and I was able to set the friction, lock it, cut, unlock and lower the log without moving.
Nice part, I can adjust the position of the porty at whatever high I want. Free of load, the porty can be lowered or rized at will just with one hand, without having to climb up there or playing with knots. But under load, the friction of the rope in the crotch locks it in place, all the slack needed for the lowering goes by the block on the log, the porty stays where it is, in the middle of the air.
