So you wanted to know about pretensioning, hence why i didn't follow when you said nc, I'm with you now. Did you sweat the line to tension it first? That usually works really well. If you need more than that you can pretension with a fiddle block but it's about the tool of last resort. The traditional way would be setting a prussic, pulling it down to tension the limb, removing slack to your rigging device, then removing the fiddle blocks then prussic. Another way is to induce a side pull with the fiddle blocks to tension like you're sweating, add a pulley in between the friction device and the top block, tie off your rigging device, tension the fiddle, and simply tie off the fiddle block line to keep the tension. In other words your fiddle block is in the tree halfway up, and simply pulls the line sideways to tension it. While much faster it's still super awkward, and will pull harder because you're using angles better, but with less potential length.
This is why rigging bollards that rotate are king. A grcs has additional ma built in, but even an old school one that doesn't have gears beats a fiddle block. You can also move your portawrap to a truck and add a pulley in the base of the tree, and convert it to a ground run setup, simply driving the truck a bit to supply the pull. Likewise you can do the same with your fiddle blocks attached to another tree or something, but you'll fight it trying to rotate on you. The trick of course is to go old school, like sailor old school, and lash a pipe or stick on it so i can't rotate. You can also use your maasdam puller to provide the pulling in either setup too, as a separate system obviously.
The other really handy trick when doing limbs that way is to cut your notch aiming to the side and pull it around with a tag line tied to the tip, this is called swinging limbs over an obstruction. This requires far less pretensioning since the hinge helps hold it up until you're in the clear. The butt will swing to the obstruction, so keeping it closely rigged is key. This is my preferred method to do limbs over a house since there's complete control over the load, but you need the headroom. Without the headroom you need to drift the loads to the trunk, once again a bollard shines here.
