Very good post, thanks!! (am hoping to get to replying in Media tonight it's in one of the tabs I just opened had a too-many-tabs internet/browser failure actually full shut-down 1st ever on this machine, anyway will be caught up soon

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As others have mentioned, it's not something you want to make a habit of... I take a Stein RC-1000 up the tree (well, pull it up with haul line) and use it on the nearest stem to where I'm cutting. Slow setting up, but I can manage it. Tie the rigging line off somewhere near you, but between you and the stem, so it's behind you. Cut, untie the line and lower. The biggest downside to this is that you can't let the piece run, because you most positively do NOT want to try to hold onto the rigging line while you make your cut! This also means you need to stick with pieces that won't knock you out of the tree or kill you if they swing back into you. If you really think about what the possibilities are for the piece when the cut is made, you can allow for all this, but again, this isn't something I would recommend anyone do. I do it when I want to get the job done and I don't have any help. These are always small jobs at relatively low heights, and I am very careful (and slow) when I do it. I'm looking to pick up one of the mini-portawraps, which are terribly lighter in weight, and will help discourgage me from pushing things. That Stein is a heavy beast.
How often do you setup a 2nd system to do 2-system rigging or drift-rigging? Have been a huge fan of @LawrenceSchultz3000 's vids lately he seems to know how to get the most out of any tree/system it is pretty amazing! Do you have any comparison between the rc1000 and a Porty? Is it more like a Medium porty? Would love to know if you've got a comparison for aerial-friction between a porty & a Safebloc!
In watching Schultz's style/approach I'm starting to think that, instead of "as-required", it should be more 'the norm' to over-compensate like that, to use a 2nd line whenever possible/practical, to almost-always setup double-whip configurations on the log being cut, I wish I had the means to test it but I'd LOVE to see the chasm between peak-dynamic-forces from the same log depending whether it was dropped by:
1 - stiff bull rope going from groundie to basal bollard to 4" block to bowline on log, versus
2 - more-dynamic bull rope (ie Nystron not Stable Braid) going from groundie to basal bollard, then through 2-4 rings or sets-of-rings en route to terminal-anchorage which is a Porty or Safebloc, then
through a Safebloc (or XL ring(s)) that are roped to the cut log, and finally back to a wrap&knot around the tree.
Would bet that ^#2's peak-dynamic-force, if you had an Enforcer load cell between the groundie's hands and the bull-rope's tail, I bet it'd be something huge like 50% force reduction, and you can of course just use a 2nd, comparable system when taking larger pieces (or when longer falls are on the menu)
Wish I could mess around w/ this type of stuff more often, only recently "finished my kit" and most of the work I do I don't get a chance to use it (even stuff that'd benefit from rigging like a speedline I can't convince the guy I do most of my work for that it's smart, he'll only allow rigging when it's 100.0% required for not breaking something never because it's smarter/easier only when a requisite thing like house-proximity) Are you 'competent person'/boss/similar in most/all of the work you do or are you working under a larger company?